It currently follows the rainbow through a gradient on a log 10 scale roughly, where 10000 sats tipped is the highest, ie purple.

<= 10 sats = orange 100 sats = green 1000 sats = blue 10000 sats = purple

I'm not sure how we'll have turbo tipping affect colors. Perhaps each click on turbo tipping will follow the rainbow too, regardless of your default tip. I still also need to figure out how it overlaps with press-and-hold custom tips.

Open to feedback if you have a preference.