Here's a little more justification to try to placate any of you who
still don't approve of the final decision.
Start by ignoring any baggage that the color names carry, and just
look at transparent Rainbow plastic pyramids. What is it that makes
each one unique?
Red is the warmest.
Green is the coolest.
Yellow is the lightest.
Blue is the darkest.
Don't think about colors in the abstract. Look at the actual
pieces. To my eyes, Yellow is too unsaturated to challenge Red for
the title of warmest, and Blue is entirely too dark to push Green
aside as the coolest.
Now look at the corresponding transparent Xeno pieces.
Orange is the warmest.
Cyan is the coolest.
Clear is the lightest.
Purple is the darkest.
That's my analysis of why the now-canonical Homeworlds mapping is the
most obvious and intuitive to *me*, anyway.
Going further, both Black and White are the most opaque in their
respective sets, so they obviously fill the same roles. And it seems
reasonable that the warm/cool/light/dark/opaque distinction ought to
be an intentional feature of a hypothetical third Treehouse set.
Cool: Aqua (Sea green)
Light: Pink (Rose)
Dark: Brown (Root beer)
(It might be fun actually to *measure* the transparent pyramids'
characteristics in the HSV color space, and see where they fall.)