Still a work in progress but just to give you an idea.

Sanded a bit too much after a few different color variations so will buy a new one now that I know what I want.



Process:

Get the color paint of your choice
Dip a q-tip in it
Push paint into the lettering
Let dry then add more
Wet sand with super fine grit sandpaper to remove excess paint

You'll be left with colored letters. You don't have to sand too hard so don't worry about your button looking like mine.

Another variation I may try is black letters with a red translucent candy apple color.

 

hard to see the difference

 

Hyp- what color are your letters? Mine were black so I can tell the difference but it is subtle, unlike making the entire button red...which I may still do.