I do not watch Critical Role and know very little about it.
However, whilst looking into different skin colours for tieflings, I discovered the characters Jester Lavorre, who has blue skin, and Lillith Daturai, who has white skin. I am curious to know what in-universe lore exists in Matt Mercer's homebrew universe to explain why these tiefling characters have the skin colour that they do. Searching online, I have been unable to find such information, simply that they are the colours that they are, not why.
I believe the Explorer's Guide to Wildemount book is out now, and I don't know if this is the sort of thing that would be in that book, but I don't know where else such lore might be found besides watching the show (or possibly statements by those involved in the show, such as Matt Mercer, etc). For reasons unrelated to this question/lore that I don't want to expand on, watching the show is not something I plan to do, but I'm still curious about the universe and the lore relating to these tieflings' skin colour.
So, from an in-universe lore perspective, why is Jester blue and Lillith white in the Critical Role homebrew universe?