Change Color of Individual Buttons

Site URL: https://star-turquoise-mzgf.squarespace.com/

I'm trying to change individual colors of buttons on my website - page noted below. I can generate outlines and change the text color, but I'm looking to just change the background of the button block. I'd like them all to be different colors. Any ideas?

https://star-turquoise-mzgf.squarespace.com/home-designing-immersive-programs 

PW: pilot 

Add to Home > Design > Custom CSS

div#block-yui_3_17_2_1_1608554061906_6771 a {
    background: blue;
}
div#block-yui_3_17_2_1_1607541617718_19582 a {
    background: violet;
}
div#block-yui_3_17_2_1_1607541617718_20245 a {
    background: red;
}
div#block-yui_3_17_2_1_1607541617718_22702 a {
    background: green;
}

@tuanphan That worked great, thank you! 

I see logo is huge so blurry on mobile. If you want to resize, add this to Design > Custom CSS

/* resize mobile ypo logo */
@media screen and (max-width:767px) {
div#block-yui_3_17_2_1_1607636525796_4682 {
    width: 50%;
    margin: 0 auto;
}
}