This is all Tinsel's fault. -x -m

[Beqanna Fairy]

Unusual colours aren't always passed on to the foal, and we decide that by dice rolls. The foal didn't roll to inherit his mother's unusual colouring fully, though he did get partial (hence the mane/tail). Without her green colouring, the mother was put as a bay (we usually choose from bay/black bases, occasionally chestnut).

In this case I can change the mother's base to black, so the foal will be black (Ee/aa).