For the lazy way use this plugin https://www.ads-software.com/plugins/text-selection-color/ its low rating but it does its job and saves time to changed the highlight’s for your site no need for messing around with or in the Edit or HTML way of your site it worked for https://fergoo.com/
& also you can stop the White Flash During Page Transitions in Google Chrome by putting this in your HEADER
Under this <!DOCTYPE html>
Easy to find near the top ??
put this under neath it
<html style=”background-color: #000000;”>
Also here is a HTML Color finder https://html-color-codes.info/ always come in handy for lots of colors to suit your themes
