Note that with the change from #20, if you try to generate a JSON schema for a model with a field of type Color, it actually errors:
pydantic.errors.PydanticInvalidForJsonSchema: Cannot generate a JsonSchema for core_schema.FunctionSchema (<bound method Color._validate of <class 'pydantic_extra_types.types.color.Color'>>)
Addresses my comment on #20.
Note that with the change from #20, if you try to generate a JSON schema for a model with a field of type Color, it actually errors: