Well as you don't know the back ground it could be almost impossible to tell, so I'd tell the new owners just that.
Give them your best educated guess, based on belly color, paw strips, eye color etc........
If the belly is dirty there's ebony there somewhere.
If there's paws stripes you have the velvet.
The shades of ebony, light, medium and dark and very distinctive, but just as with our hair color there can be a lot of in betweens. Especially if there hasn't been a good standard in there for several generations back. Mish mash.
I would also recommend these mish-mash chins not be bred. Your only breeding more and I feel my goal as a breeder is to keep the lines strong.
I know,
I have seem some really cute mixes that I'd love to have, and have been told hobby breeders don't have to be so picky.
As pets it really doesn't matter, but to me it does.
I look at all the mixed breeds of dogs out there now and wonder will we loose breeds all together because some thought a beagle colors would look good on grey hound..
But you know what I mean.
Be honest, your really not sure
That first one is a med. ebony.... my Leona again , she haunting me now for talking about her