Lines here for anyone else who wants to colour this.
Twilight is supposed to have a slightly sickly paleness to her because she often stays up (too) late, whereas Rarity carefully nurtures hers with sun-blocker ;)
Rainbow Dash and Applejack both have a tan because they’re often out in the field (either doing sports or tending to the farm).
Same for the CMC (save Sweetie Belle, who is a little bit more sheltered)
Spike has a slightly green-ish complexion because he’s a dragon :)
If anybody else wants to take a stab at colouring, they can download the lines here.
I got the suggestion to draw the mane 6 with their destinies/clothes swapped. To say I had fun drawing this is way of an understatement.
edited the timing and removed the breathing animation - i’ll have to figure that one out properly sometime.