is it posible to change the color of the light under the A/C controls and under the P,R,N,OD,D,2,1 shift pattern on my automatic 91RS?

 

yup
its a 68 or a 94 bulb i beleve

 

I'm not sure which bulb the "book" says, but I used a leftover 94 xenon bulb from my dash mod project. it's been 6 months with no problem...what color are you gonna use? You said 91 right? are the markings yellow? Mine are white in my 89 so I had no problems, but if yours are yellow, i don't know how well a different color other thatn white would look
...yellow and blue make green...etc.etc.