I'm not sure why you're not getting color. The composite setup (red, white, yellow) might be offering black and white setup due to a setting, but if it's happening to both DVDs and PS3, then it sounds like a bad port.
Component would be the way to go - Red,Blue,Green+(red+white audio) for both of those applications to get a better picture. Your color spectrum through that connection would be significantly better.
Still, there's no reason I can think of why you're getting only a black and white picture with both your PS3 and DVD - and in that case, it leads me to believe that the ports may not be working.
Help, my new tv wont play dvds or play station 3 in color. I am using the red,wht,and yellow cable set up. That works on my old tv, why wont it work on this one? I have found no settings on tv to change in the menue. This is my first lcd tv. Is it the cable system I am using. If so why dont they let you know this?