ISO: Natural food colouring

I'd like to make a red velvet cake this weekend (to help celebrate Chinese New Year) and was wondering if anyone knows where I can buy natural food colouring in the downtown area. I know that sometimes beet juice is substituted, however I'd prefer not to use that as it may alter the taste. I'm thinking of checking Whole Foods and possibly Fiesta Farms, and I'm guessing perhaps some cake decorating stores may carry it, but if anyone knows for certain where I can purchase it please let me know!