Location of mouseover/hover effects on icons-only task manager?

I was wondering if anyone could tell me where the location for the icons-only task manager settings file is for plasma? I have a number of custom icons I’ve made, and it appears that the default mouseover/hover effect does not work with them. For icons I have not changed, the icon “lights up” or gets a wash over itself when I hover over it, but the custom icons don’t do that. There doesn’t appear to be anything in the .svg files, so I’m wondering if there’s a master list that I should add my icon files to or something, perhaps in the theme settings? I apologize for what is probably a fairly silly post, but I’ve been enjoying mildly customizing my desktop and this is a bit of a annoyance.