VCR Gymnast wrote:

A portable Beta VCR (Toshiba V-X340) from 1985 works perfectly except
there is no color:

1. Pre-recorded color tapes play back in B&W
2. Tapes recorded on this VCR play back in B&W on this VCR
3. Tapes recorded on this VCR play back in B&W on other known good VCRs

Therefore, the VCR can neither record nor playback color signals.

The machine has no switch for B&W/Color and the 3.58 MHz oscillator is
not out of adjustment. I have checked out all of the Chroma circuitry
and all measurements are within the range stated in the Service Manual.

Could it be the video heads even if the B&W picture is flawless?
If not, what else can be tried?

Just a shot in the dark, but have you tried playing the VCR on a different
TV? I'm thinking that if you've only played it on one TV it might be a
problem with that TV and not a problem with the VCR.