Blue hair didn't always come naturally
On the days he hated his parents for dying,
He'd come in with Harry's black hair,
Ron's long nose.
The day Victoire Weasley got Sorted,
His hair involuntarily turned the pale blonde,
And only McGonagall noticed.
There were a distinct lack of redheads around when Lily Luna arrived
So that problem was fixed for a year
But when he finally develops his own identity:
He tries out blue hair
And it's odd
And Andromeda thinks it's a phase
But it's perfect