Fit and functionality are more important to me. That said I don't favor white, so when I have a choice it's usually beige, gray or black.
Since nobody will see me in my underwear I don't worry about matching colors. When I see it on somebody else, if a strap shows I don't even notice if the color matches.
Showing through a light-colored top can be part of your fashion statement, so dark under light may be what you want.