I don't see why people can't just accept the fact that people like different colors... not everything has to be a symbol, guys.
Light Jedi typically like blue and green because the color is more smooth and pure.
Dark Jedi typically like red because they are generall hateful, deceitful... and accordingly, typically like the color red.
And Mace just wanted to be different! Fits in that way in terms of the movie and the actor too.