many cameras have CCU's that offer the ability to give you color correction for blacks, gains and gammas. There are plenty of third party companies (cobalt digital, For-A, etc.) that make stand alone color correctors. But you need to buy THREE of these. If you think that you are going to get a 3 channel unit for "cheap money" all in one box, it's not gonna happen.
You didn't say what camera you were using, or if it was composite, component, SDI, or HD-SDI.