I've got a date for prom. I've got a year till prom, I was wondering when shall I look for suits and all for prom?

I am guessing since you said a suit, you are a guy. Most guys I know rented a tuxedo for prom. The color of your tie or any other accessory such  as a vest, would be the color of you dates dress. Personally i like just the tux, a tie and the pocket silk. Clean and simple and you are not competing with your date. You want to complement your date and her outfit, not compete with her.