I submited my vote in favour of the 2 colors but don't take it wrong, i love both.
To get to the point:

2 colors: more practical and easier to implement.

3 colors: a bit more work arround it but looks pretty and refreshing

My opinion/suggestion?

If it could be posible to IMPLEMENT BOTH and let the user decide(making it clientside, if thats even posible)
It,s a shame to discard either of them, one looking so beautiful and the other so clasical and practical. (And also the work that has been put in both of them, the devs who did it... deserve it)

Sorry for the pretty basic english with typos

I loved jet and power adaptor when i used them in the "CBM" mod, glad to see them in vanilla with interesting graphic aditions and quirks!! Can't wait to try them!

Fiuf, I haven't been here for so long that my user got deleted hahaha
Nice to see this wonderful project is still going!
That Magnet Beam looks fun to use, will allow players to do many weird shenanigans!
Love those map revamps that still keep the original feeling of them intact.

Good luck to the team developing it!!