Change the Color Theme of One Event?

We have a Halloween event coming up and I'd like to change the color theme of that event to my "Darkest 1" theme. However, when I change the color on the event page (which I'd like to keep my "Lightest 1" theme), it changes my Events Page colors as well. Is there a way to change the colors of one specific event? Attached are images of what I want the two pages to look like.

Add this code to Website Tools (under Not Linked) > Custom CSS

body#item-6515aefaccc770706876bba9 {
& {
    background-color: black !important;
}
section, .section-border, .section-background {
    background-color: transparent !important;
}
.header-nav-item>a {
    color: white;
}
.content-wrapper * {
    color: white;
}} 

with body#... is owl-o-ween Page ID