I can be any color you can imagine.
You see me in everyday life.
I have been around for many, many years.
Look around you.... You can probably see some of me right now.
BTW, I'm having some connectivity issues right now. I'll post answers as soon as I can.
The written word? For example - 'red', 'blue', etc.
Although clothes seem to fit the bill somewhat as well.
I was thinking a little more pedestrian than light. I had paint as the answer, but clothing certainly works.