Has everyone asked you "what are your colors for the wedding?" How annoying, and yet, how necessary for the entire scheme of your event! Blue? Green? Red? It all can convey the feeling of the day!
A bride asked "does the Save the Date card have to match the invitation?" Well, the answer is "no." At the time you need to send out the Save the Date, you probably don't even know what the invitation is going to look like, none the less, what colors, etc. Just so long as they both have your personality and style, they do NOT have to coordinate.
Remember, the save the dates are just to let your invitees know when and where you plan on getting married. They do not need to give details or exact information... send them out as early as you can. As early as 12 months ahead, if possible.
FYI... a bride I know had planned on blue dresses for her bridal party..., when they were no longer available, she moved on to a GORGEOUS bright green. She matched all her flowers accordingly, and voila... the perfect color match!