so how about my headcanons:
 
twilight is dark-skinned swedish  
rarity is pale-skinned french  
rainbow dash is peach-skinned american (probably california state)  
fluttershy is light-skinned italian  
applejack is ‘light pink with peach’-skinned american (texas) with slavic roots  
pinkie pie is pink-skinned slavic (probably ukranian)  
tempest is dark-skinned african with asian roots  
cadance is pale-skinned japanese  
scootaloo is dark-skinned american (the same state as RD)
 
all of them are cis-women (well, scoot is cis-girl, anyway :D)
 
I based on their original color-palletes and tried to pick up the closest skin-tone and I actually like the result hehe