I have a sorrel and a dark bay/brown.
Sometimes I like to use the same colour tack, with a reddish leather on the sorrel and a darker mahogany on the bay. Sometimes I like the contrast.
It's really up to you, your preference and what type of riding you intend to do. For example, when showing, you conform to what that standard is. For trail riding, you put on the bridle you feel you like that day.
Some pictures would be nice.