My two cents,
Well, it seems to me that dictionaries might have varied a wee bit on this, and I've seen various opinions in writing-craft related books about this (not sure what CMOS says, if one of their editions had talked about it), anyway ... The way I've tended to look at it (and still do, though perhaps even stronger now, especially for fiction) is that: blonde is used for both adjective and noun for female stuff, while blond is used for both adjective and noun for other stuff (male and neuter).
(Edited-to-add: Though when I was very young I had opined for "A blonde has blond hair." But no longer do I. Perhaps, in that situation, both could be acceptable to most: "A blonde has blond/blonde hair"; but the following would not be acceptable: *"A blond has blonde hair.")
That's the way I write and read fiction. An editor best not screw around with my usage of it in my fiction, not if he wants to keep the rest of his nine digits intact. And so, if I read the following (especially if fiction),
So a blonde hostess might seat you, but a blond took your order.I'd be wondering, "Hey, where'd that dude come from?"
Of course, this is my personal preference. And perhaps if the writer is writing for a publisher whose style guide says something different, then that would probably be a different type of sort of thing.