Call him any colour - he is just gorgeous! He reminds me of a rocking horse that was in an antiques shop near my gran's when I was very young. I really wanted it but it was too expensive!
I'm pretty sure blue roan is incorrect...Roans don't go dappled or grey out..they stay roan..I imagine when he was younger he was iron grey like this pony:
Grey- A roan has a base colour face. -not greyed-
And does not chnage or get lighter each year, only a summer colour, a winter colour and a clipped colour.
Varius types of grey and rose grey and iron grey are not roan -which comes from a gene that modifies the base colour of bay, chestnut or black, but, oddly, does not affect the front of the face.