From the '86 supra that i've worked on:
-that as far as the gauge cluster lights, they are just bulbs with colored covers over them, just remove some molding and then the cluster and the bulbs screw in from the back. Just change the color of the rubber sleeves. As far as subies...unless they have updated the tech (don't know myself
), it is probably similar
-changing digital readout colors (IE, clocks and such) is virtually impossible as far as I know without changing the gauge itself.
-LCD displays like the radio and CD players will have to stay stock backlit unless they are replaced with aftermarket ones (as far as i know anyway)
Some of my info is probably a bit dated...but i hope it helped at least a little bit.