How rare are red/orange manx cats and are males more rare than females? Are more hypoallergenic?

Actually, for red cats (often colored orange), the ratio of males to females is about 4:1. A red boy can be XY, while a red female has to be XX, which is less common.

As far as Manx cats, there are really two ways of looking at it. A manx can be simply a domestic kitty with no tail, or could be a cat descended specifically from the Isle of Man, meaning purebred.

And a purebred Manx cat can give birth to a kitty that has a tail.

There really are no such things as a 100% hypoallergenic cat, only shades of eliciting less of an allergenic response. Most people are allergic to the dander, which are dried saliva and skin cells, so it is the protein in the saliva that is usually the problem. There is no reason to think Manx cats would fit into any particular category as far as allergy response.

Orange Manx Cat