What I am saying is that there is the consideration of the possibility of reversed polarity damaging the illuminating LEDs.
Given that we have no information at all about the LED arrays shown in post #1 there is no way to give good advice. The best I can give is a guess.
That circuit shown in post #1 includes four diodes, which the arrangement is intended to prevent the application of reverse voltage to the LEDs that are not to be illuminated. IF that group of LEDs is installed as part of the light fixture assembly that we have no information about.
In that case, the system could possibly work fairly well with only two wires connecting the three position switch to the light fixture.

My comment in post 19 was based on the idea of adding a fair amount of electronics that I was not about to try explaining. We have no explanation as to the TS understanding of electrical circuits.

 

Thank you for your input, Being a total novice to this, I'm happy to have all opinions presented. My understanding is limited.

 

It can not happen in a simple manner. Can be done, not with diodes, though

The original circuit does it. That is the entire point of that circuit.

If the top wire is plus, the white LEDs light. If the bottom wire is plus, the yellow LEDs light. The DPDT switch reverses the polarity fed to the lights.

 

Just for fun and giggles here's an alternative using a relay thus eliminating the voltage drop through the diodes.

 

Just for fun and giggles here's an alternative using a relay thus eliminating the voltage drop through the diodes.
View attachment 307793

This is indeed an interesting concept, the challenge being to add a SMALL continuous duty 12 volt relay able to handle the load. The challenge being for the relay to be adequately rugged for the application. It does make an assumption about the light that is reasonable, though.