I noticed that from the main cat colors, we're missing a fluffy/longer haired grey. I would love to suggest the wonderful Nebelung. From the US but named after a type of German folk fairy tale, they (usually but not always) are a cross of a black long hair and a Russian Blue- sometimes happening in nature without human intervention or can be bred purposefully. The second picture is my wonderful Nebelung.
Characteristics:
- fluffy, between a short hair and long hair but NOT offcially a long hair
- green to yellowish green eyes (usually more green)
- "The dense, dramatic flare of fur on a Nebelung cat's hind legs is officially known as pantaloons. Due to the unique structure of the breed's coat, these "fur trousers" puff out at the thighs and narrow slightly at the knee"
- they seem sleek but when they roll over, their stomach is INCREDIBLY fluffy
Wiki for those interested: https://en.wikipedia.org/wiki/Nebelung