While this is usually a complete set of reasons for this problem, a) it was Thursday and TODAY is Friday, and b) the sets worked when we got there.

Lowhz,
There were no cable reversals. We watched that very carefully, then exhaustively checked cabling connections. What we got was this:

The TVs worked before we started doing this.

On the first TV:
Often but not always, green only gave us nothing. Sometimes it gave us the garbage screen (with an overall pink look). This screen had five rectangular areas across the bottom that looked different.

Sometimes when green gave us nothing, addition of EITHER red or blue gave us the garbage screen.

Use of the red cable for green out of the switch to green in on the TV gave us the same results. Use of the blue cable the same way gave us the same results.

What's most remarkable about this was that we got color out of the TV with only a green input.

Two times we got a mostly black screen with a deep purple color across the top that turned to black by halfway down the screen.

On the second TV:
Similar behavior, with these additions:
We didn't always get the garbage screen. The garbage screen had an overall greenish look.

This TV was being sent the output of a DirecTV box that worked properly on the other RVs. ) With only green, when we didn't get the garbage screen we got a nice white and blue DirecTV logo, with about a dozen vertical white lines an inch each across, from the midpoint of the TV to the top.