After some editing, I found that while pure color does work, trying to make them look "dark mode" or KSP2-esque resulted in them having a blue hue. Later, I found that coloring these dark grey to white also retains the hue.
I have been having a lot of fun messing around with textures and whatnot!
While experimenting, I found that the editor category buttons (edcat_btn_generic_...) (specifically normal and over, potentially disabled and active) have some set color that cannot be edited with the current config. Would it be possible to make these textures recolorable?