The purples are really good stars but rare (about PQ 26?). On the 0 to 14 planets I have not noticed a correlation with the star color and planet quality. When I colonize 13 & 14 (and 12 with the 5% PQ choice), I get all kinds of stars of different sizes and color.
Purple stars are yellow stars with an influence bonus, but no bonus to PQ far as I can tell. Purple and yellow always have PQ 15+ planet, yellow stars seem to be worth ~10 influence, and purple ~20.
Notice that when a minor race appears, they convert their star to yellow. I want that tech 8-)
Every other star, regardless of color, will pretty much suck. Rarely, however, you will find a star system with ~50 influence, supposedly from Precurser left overs. Have a party there!
After reading Rabid Bob's post, I should have said that the purple stars I have seen have been higher PQ. But since I have only played about 20 games and not seen many purples, my observations may not extrapolate to whether all purples are good PQ. On the other hand, since I colonize PQ 13 & 14, I can't say they "suck". To me the "it sucks" category belongs to those stars who have no planets that you can't get to PQ15 or more even with both Soil & Habitat 10% PQ bonuses.
Colonizing the sub 15's is a bit of an ongoing argument, it seems
My take (which is why I say they suck ) is that the sub 15's aren't ever gonna be able to pay well or produce well. GalCiv is set up so that high PQ planets will perform a lot better. After awhile, heck, even those PQ 15 planets start to seem wimpy
All that aside, though, there are times when those sub 15's become attractive. Especially when I'm a long way from being top dog in the galaxy
I just tried your improvements. They're fun! But probably not for the long term, at least for me. The main thing is that it's unbalancing: the AI doesn't realize that Improved Environmental Control is now a great tech, and doesn't research it until late game.
[Message Edited]