1) I'm not entirely sure what the different colours mean but it might be linked to special scenes or completed story lines
2) there is currently no way to reach passion/lust 5 so it will probably be adressed in an update or removed
3) go to the right room in the bunny manor, safe and reset after placing your bet until you find the jackpot (40G for a 10G bet), visit your favourite girl ella because she will convert 10G into 1 goddess coin, repeat until you have enough goddess coins