I love using colorful matting with artwork. It's an easy change - you could obviously get new mat board cut, but consider painting out your white mat (I've had great success with those $1 bottles of craft paint), or maybe investing in a $30 mat cutter to experiment on your own. Also, I see vintage and antique artwork with colorful mats at flea markets all the time. Here's a piece my client and I found at a flea market in Pennsylvania (or was it NJ, Sheila?).

One of my favorite colors - that emerald green! I think it's so pretty with the black and gold accents.

I have a big art wall in my dining room. To mix it up a little I've been adding colorful mats to the group. Most of the frames have cream or white mats still, but I'd like to have four or five frames with colorful matting eventually.

I bought this piece at Housing Works for $10:

These pretty pink pictures were spotted at Alt in the ladies room at the Grand America.

Another pretty emerald green mat at a gallery near my house: