Received an email from a collector of one of my watercolor paintings on paper. She had a question about how to find the right mat that complements and ties together the look of both the painting and her decor. The following answer is based on my own experience in searching for the right mat. Maybe this will answer some your questions as well:

Hi Sally,
The best way I know to get the right mat for your artwork and your kitchen decor is to spend a little time at your local frame shop. Most framers are knowledgeable about helping you find the right color combination. They have color mat samples in an L shape, so that you can see how a certain color works next to the artwork.
Bring in your artwork, frame, if you already have it, and a color sample of the room it will be hanging in.   The sample can be a paint chip sample from the paint store or even a dish or vase that has your room colors on it. This is how interior designers do it and I think it will help you to get the right mat.
It really comes right down to personal taste. You have to be the final judge on whether the mat looks good in your eyes. Seeing all the pieces next to each other before you make the final mat choice helps you to narrow down your options very quickly.
Hope this answers your question and please don't hesitate to write if you have further questions or concerns.
Best Regards,
Blenda