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It is possible that the TV was hit by a small power surge, and the processor has some garbage in it, and you need to leave it unplug for 40 MIN, and that will reset back to normal.
Also after that if it is still black and white, then by pass the tuner and feed the signal directly to the video input,,and see if the color works if so then you need a tuner. If you still have no color then it could be the co;or processor IC or the crystal in the color section needs replace.