OK, second attempt as this flipping forum ate my answer, YET AGAIN!!
I apologise for confusing the issue yesterday, my only explanation is that I was on new pain meds and, five minutes after posting, was crashed out in bed, fast asleep, so I am sorry about that!!
Anyway,
you are talking about a dominant, as opposed to recessive, gene, but this is not to say that this colour/modifier/pattern is Dominant over all other colours/patterns /modifiers.
It will still only show up 50% of the time unless it is H/Z.
It is a
simple dominant gene, but it is not Dominant over all others, (although, actually, I will have to check on whether or not it is simple!) not in the way the OP meant, anyway.
Grey shows up when it is h/Z, so does Black, so when it is present, it is expressed, regardless of zygosity.
Yes, we can agree on that.
Grey does not show up more than 50% of the time unless it is H/Z, it is not Dominant in that way.....
Is that any clearer?
Honestly, I am sorry, it seems to be OK inside my head, but when I get it out on the paper it does not seem to make a lot of sense.
Nothing new there, then