Rca big sreen went black and white menue is still in color
Try using one of the other video input options, like AV inputs. If still have black and white picture, then the color processor is having issues. If now in color, then your tuner has issues detecting the chroma / luminance signal.
If you are using an external digital box, this may be the source of the problem as well. If you still have a VCR, connect the coax from VCR to the coax input on the TV, and play a tape. Tune the tv to channel 3 or 4. If in color, then your set top digital box is faulty.