What this issue is describing is the little paint splotch icons on the top right of items aren't animated if they have paint spells applied.
Shown below is my killer exclusive with spectral spectrum and it's little paint splotch in the corner, if I hop out of my loadout and then go back into it the color of the paint splotch changes but remains static.

Clicked back into my medic loadout and the paint splotch icon is a different color now.

I think it'd be cool if these little splotches were animated provided the item in question has a paint spell applied.