"rufousing polygenes" are theorised to be the reason for this variance.Orange is epistatic to non-agouti, so all red cats are tabbies. "Solid" red show cats are usually low contrast ticked tabbies.

The identity of the gene at the Orange locus was narrowed down to a 3.5 Mb stretch on the X chromosome in 2009. In 2024 it was discovered that the dominant orange colour associated with the Orange locus is the result of a genomic deletion in a regulatory region of , a Rho GTPase