LG 42PX4DV- black and white through external imputs only

Hello freudianslip,

Since you said that you moved the TV set and then this problem occurred, this leads me to believe that this is a case of mechanical failure (cold solder connections). I say this because so rarely does moving a TV cause a failure in the electronics of the TV.
Now to fix this problem one might suggest that you take a soldering iron and some solder and start locating the possible cold solder connections and touch them up. I will not suggest that, because most sets now have SMCs (surface mounted components) which require specialized equipment to remove or to refinish soldering work, even with the right equipment there is a chance of doing real damage to the TV set.
I say, since you know the approximate area of the problem (DVD inputs RCA Ports), you should relay this to a qualified TV repair person and then have them troubleshoot and repair this problem. I know this was not what you wanted to hear since this is a fix it yourself site, however as a owner of a TV repair shop I have had many people bring their sets in after effecting repairs on complicated electronics because someone gave good advise, but the skill level of the TV owner was not up to the level of the person giving the advise.

One the off chance that this is an electronics problem my guess would be the video processor section, in which case taking it to a TV repair shop is a wise decision also for the same reasons mentioned above.

I hope this helps
Thank you,
Shuttle83