If you have ever opened up you gauges completely you'll see that every indicator is painted a different color...battery is red, turn signals are green and so on. They did this so they would not have to use different colored bulbs for each application and just use white bulbs for everything.
Noooooow, if you wanted to switch the color of something you would be able to. Like FF40 mentioned making the turn signals blue or red. You would have to take your gauges completely apart, remove the lens, needles...blah blah blah. Then you would pry the backing off, the backing is what all the numbers and so are printed on, you would have to turn it over and you will see that the turn signals are green, just sand them down until they are see through, now you can put in blue or red LEDs and you will now have blue or red turn signals.
Yeah, confusing I know. I'll see if I pry mine apart and take some pictures. Is not as complicated as it sounds.