The thought process or reasoning behind pairings

[Aercadia]

One thing I've noticed is that when a new morph shows up, the first thing people do is put it to pastel.

Part of the "game" seems to be Bold is Better, so it makes sense that the first thing into a new morph is something to crank up the brightness. I think it's pretty intentional - you crank it up a level with Pastel, and then you can double it with super Pastel... other common enhancements seem to be Fire, Vanilla, Enchi. Or on the darker end of the spectrum you've got Cinnamon and Mojave - those Mojave GHIs are no joke!