I would describe him as grey and put a photo in so people can make their own judgement as to what he will be, they cannot then say you have not described him correctly
I would just say grey. He definitely is going to grey out to something (look at that tail!) so it's the most accurate. Besides, there isn't much point worrying what type of grey he is, they all end up white in the end! lol
Where does he get the grey gene from? His father? 'Cos if the chestnut is his mother, he takes after someone else I would put 'dark grey at present' to cover yourself. My jet black boy was born with a grey tail too , and I wondered what colour it would end up. He is a pretty sort though. Good luck.
Thankyou for all your suggestions. His mother was a fleabitten grey connemara although I dont know what colour she was before she greyed out, his sire was a dark bay hanovarian.
suzi your grey is lovely all clean and smart.