kasper.arlund

I managed to write a code using Jquery. It's not to most elegant way,  basically its made to click the next arrow in the slideshow every couple of seconds:
 
<script src="//ajax.googleapis.com/ajax/libs/jquery/2.0.2/jquery.min.js"></script> <script> const init = () => { setInterval(() => { $('.gallery-reel-control [aria-label="Next Slide"]').trigger('click'); }, 6000); // change this value to change the speed } document.addEventListener('DOMContentLoaded', init); </script> You can insert this into Code Injection or in to the Advanced section of the specific page the Slideshow is on.

I haven't tested if this works on any other gallery types by the way.

(Updated: SS 7.1)
Some custom code (CSS) to change color
Navigation Link Navigation Hover Link Navigation Active Link >> 92 Templates Navigation Custom Font
Notes
Add code to Home > Design > Custom CSS The code is based on demo at squarespace.com/templates, so they may not work for some websites or navigation with dropdown If the code doesn't work, try adding !important to after, eg: color: #f1f2f3 !important; If you have any questions/found issues, just comment below or send me a private message. Thanks. Avenue Template
/* Nav item color */ .main-nav ul li a { color: #ff0000 !important; } /* Nav item hover color */ .main-nav ul li a:hover { color: violet !important; } /* Nav item active color */ .main-nav ul li.active-link a { color: green !important; } Aviator
/* Nav item color */ nav#main-navigation ul li a { color: #ff0000 !important; } /* Nav item hover color */ nav#main-navigation ul li a:hover { color: violet !important; } /* Nav item active color */ nav#main-navigation ul li.active-link a { color: green !important; } Bedford Family: Anya, Bedford, Bryant, Hayden, Bedford
/* Nav item color */ #mainNavigation div a { color: #ff0000 !important; } /* Nav item hover color */ #mainNavigation div a:hover { color: violet !important; } /* Nav item active color */ #mainNavigation div.active a { color: green !important; } Brine Family: Aria, Basil, Blend, Brine, Burke, Cacao, Clay, Custom Template, Ethan, Fairfield, Feed, Foster, Greenwich, Hatch, Heights, Hunter, Hyde, Impact, Jaunt, Juke, Keene, Kin, Lincoln, Maple, Margot, Marta, Mentor, Mercer, Miller, Mojave, Moksha, Motto, Nueva, Pedro, Polaris, Pursuit, Rally, Rover, Royce, Sofia, Sonny, Sonora, Stella, Thorne, Vow, Wav, West, Brine.
/* Nav item color */ .Header-nav-item { color: #ff0000 !important; } /* Nav item hover color */ .Header-nav-item:hover { color: violet !important; } /* Nav item active color */ .Header-nav-item--active { color: green !important; } Farro: Farro, Haute
Same as Brine
Five
/* Nav item color */ nav#main-navigation ul li a { color: #ff0000 !important; } /* Nav item hover color */ nav#main-navigation ul li a:hover { color: violet !important; } /* Nav item active color */ nav#main-navigation ul li.active-link a { color: green !important; } Flatiron
/* Nav item color */ ul#nav li a { color: #ff0000 !important; } /* Nav item hover color */ ul#nav li a:hover { color: violet !important; } /* Nav item active color */ ul#nav li.active-link a { color: green !important; } Forte
/* Nav item color */ #topNav ul li a span { color: #ff0000; } /* Nav item hover color */ #topNav ul li a:hover span { color: violet; } /* Nav item active color */ #topNav ul li.active-link a span { color: green !important; } Ishimoto
/* Nav item color */ #topNav #nav li a { color: #ff0000; } /* Nav item hover color */ #topNav #nav li a:hover { color: violet; } /* Nav item active color */ #topNav #nav li.active-link a { color: green !important; } Momentum
/* Nav item color */ #topNav ul li a { color: #ff0000; } /* Nav item hover color */ #topNav ul li a:hover { color: violet; } /* Nav item active color */ #topNav ul li.active-link a { color: green; } Montauk: Julia, Kent, Montauk, OM
Same as Momentum
Native
/* Nav item color */ #navBlock ul li a { color: #ff0000 !important; } /* Nav item hover color */ #navBlock ul li a:hover { color: violet !important; } /* Nav item active color */ #navBlock ul li.active-link a { color: green !important; } Pacific:  Bryler, Charlotte, Fulton, Horizon, Naomi, Pacific
/* Nav item color */ #mainNavigation div a { color: #ff0000 !important; } /* Nav item hover color */ #mainNavigation div a:hover { color: violet !important; } /* Nav item active color */ #mainNavigation div.active a { color: green !important; } Skye: Foundry, Indigo, Ready, Skye, Tudor
/* Nav item color */ .nav-blocks-wrapper div a span { color: #ff0000; } /* Nav item hover color */ .nav-blocks-wrapper div a:hover span { color: violet; } /* Nav item active color */ #mainNavigation div.nav-link--active a { color: green !important; } Tremont: Camino, Carson, Henson, Tremont
/* Nav item color */ #mainNavigation div a span { color: #ff0000; } /* Nav item hover color */ #mainNavigation div a:hover span { color: violet; } /* Nav item active color */ #mainNavigation div.active a span { color: green; } Wells
/* Nav item color */ div#topNav ul li a { color: #ff0000 !important; } /* Nav item hover color */ div#topNav ul li a:hover { color: violet !important; } /* Nav item active color */ div#topNav ul li.active-link a { color: green !important; } Wexley
/* Nav item color */ #topNav ul li a { color: #ff0000; } /* Nav item hover color */ #topNav ul li a:hover { color: violet; } /* Nav item active color */ #topNav ul li.active-link a { color: green; } York: Artesia, Flores, Harris, Jasper, Jones, Lange, Shibori, Taylor, York
/* Nav item color */ .site-navigation div a span { color: #ff0000; } /* Nav item hover color */ .site-navigation div a:hover span { color: violet; } /* Nav item active colo */ .site-navigation div.active a span { color: green; } Squarespace 7.1
/* Nav item color */ .header-nav-item a { color: #ff0000 !important; } /* Nav item hover color */ .header-nav-item>a:hover { color: red !important; } .header-nav-folder-item:hover a { color: red !important; } /* Nav item active color */ .header-nav-item--active a { color: green !important; } Created by Tuan Phan.
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If you want to use custom font for Navigation, just copy - paste the following codes.
Add code to Home > Design > Custom CSS
92 Templates Navigation Link Color - Hover - Active Color Avenue
@font-face { font-family: your-font-name; src: url(enter your font name url here); } #topNav nav ul li a { font-family: your-font-name; } Aviator
@font-face { font-family: your-font-name; src: url(enter your font name url here); } nav#main-navigation ul li a { font-family: your-font-name; }  
Bedford Template Family
Include: Anya, Bedford, Bryant, Hayden, Bedford
@font-face { font-family: your-font-name; src: url(enter your font name url here); } #mainNavigation div a { font-family: your-font-name; }  
Brine Template Family
Include: Aria, Basil, Blend, Brine, Burke, Cacao, Clay, Custom Template, Ethan, Fairfield, Feed, Foster, Greenwich, Hatch, Heights, Hunter, Hyde, Impact, Jaunt, Juke, Keene, Kin, Lincoln, Maple, Margot, Marta, Mentor, Mercer, Miller, Mojave, Moksha, Motto, Nueva, Pedro, Polaris, Pursuit, Rally, Rover, Royce, Sofia, Sonny, Sonora, Stella, Thorne, Vow, Wav, West, Brine.
@font-face { font-family: your-font-name; src: url(enter your font name url here); } .Header-nav-item { font-family: your-font-name; }  
Farro
Include: Farro, Haute
@font-face { font-family: your-font-name; src: url(enter your font name url here); } .Header-nav-item { font-family: your-font-name; } Five
@font-face { font-family: your-font-name; src: url(enter your font name url here); } nav#main-navigation ul li a { font-family: your-font-name; } Flatiron
@font-face { font-family: your-font-name; src: url(enter your font name url here); } ul#nav li a { font-family: your-font-name; } Forte
@font-face { font-family: your-font-name; src: url(enter your font name url here); } #topNav ul li a span { font-family: your-font-name; } Ishimoto
@font-face { font-family: your-font-name; src: url(enter your font name url here); } #topNav #nav li a { font-family: your-font-name; } Momentum
@font-face { font-family: your-font-name; src: url(enter your font name url here); } #topNav ul li a { font-family: your-font-name; }  
Montauk Template Family
Include: Julia, Kent, Montauk, OM
@font-face { font-family: your-font-name; src: url(enter your font name url here); } #topNav ul li a { font-family: your-font-name; } Native
@font-face { font-family: your-font-name; src: url(enter your font name url here); } #navBlock ul li a { font-family: your-font-name; }  
Pacific Template Family
Include:  Bryler, Charlotte, Fulton, Horizon, Naomi, Pacific
@font-face { font-family: your-font-name; src: url(enter your font name url here); } #mainNavigation div a { font-family: your-font-name; }  
Skye Template Family
Include: Foundry, Indigo, Ready, Skye, Tudor
@font-face { font-family: your-font-name; src: url(enter your font name url here); } .nav-blocks-wrapper div a span { font-family: your-font-name; }  
Tremont Template Family
Include: Camino, Carson, Henson, Tremont
@font-face { font-family: your-font-name; src: url(enter your font name url here); } #mainNavigation div a span { font-family: your-font-name; } Wells
@font-face { font-family: your-font-name; src: url(enter your font name url here); } div#topNav ul li a { font-family: your-font-name; } Wexley
@font-face { font-family: your-font-name; src: url(enter your font name url here); } div#topNav ul li a { font-family: your-font-name; }  
York Template Family
Include: Artesia, Flores, Harris, Jasper, Jones, Lange, Shibori, Taylor, York
@font-face { font-family: your-font-name; src: url(enter your font name url here); } .site-navigation div a span { font-family: your-font-name; }  
Squarespace 7.1
Include: Novo, Pazari, Nolan, Utica, Cami, Matsuya, Nevins, Kester, Gates, Zion, Classon, Hawley, Suhama, Elliott, Otto, Tepito, Balboa, Beaumont, Quincy, Talva, Minetta, Falodu, Hester, Crosby, Ventura, Maru, Tresoire, Almar, Alameda, Patil, Stanton, Paloma, Fillmore, Palmera, Souto, Brower, Merida, Grove, Harman, Rivoli, Noll, Bergen, Degraw, Corrigan, Sackett, Lakshi, Pulaski, Suhama, Cailles, Colima, Barbosa, Clune, Irving, Suffolk, Clarkson, Lusaka, Bailard, Malone, Roseti, Euclid, Carmine, Wycoff, Harbor, Ocotillo, Fayette, Roseti, Dario, Soria, Morena, Rey, Lenoix, Bleecker, Vandam, Cruz, Kitui, Waverly, Vance, Orina, Chotto, Auburn, Juniper, Palmer, Atlantic, Iduma, Pine, Eldridge, Pulsaki, Amal, Suhama, Hart, Carroll, Noll, Hidano, Palermo, Cailles, Archer, Kearny, Sellwood, Essex, Mason, Gramercy Studio, Cole, Devoe, Randi, Zorayda, Manor Studios, Grant, Toledo, Hoyd, Troutman, Tantillo, Maqueda, Hemlock, Bogart, Florence
@font-face { font-family: your-font-name; src: url(enter your font name url here); } .header-nav *, .header-menu-nav * { font-family: your-font-name; } Made by Tuan

@CaptainMaze Add to Home > Design > Custom CSS
.homepage .header-announcement-bar-wrapper { background: rgba(0,0,0,0) !important; }