fryguy:

I was looking into the same thing recently...
Believe it or not a VERY high end designer taught me a trick that worked fantastically! Assuming you have a white grill now, buy a pair of women's nylon stockings and stretch them over the grill cutting off the excess. The tighter you stretch the nylon the fainter the color. I was able to exactly match the colors of my walls and it looks and sounds great.

Good luck,

Slick