I think most automotive stores sells the color condoms, I actually took off my blue ones when I had white faces.... I tried it years ago without the blue condoms, and the color was really gross looking (to my taste) I'll post a pic of it when I get home. If anything, try taking off the condom that's on the bulb, and use a red sharpie (or whatever color floats your boat).

now I am thinking about taking out the bulbs entirely because they really shine out the reverese gauges I put in.