The agouti alleles affect which hairs and which parts of hairs produce eumelanin and which produce phaeomelanin.
All of the phaeomelanin areas in the coat of any of the agouti series patterns can be affected by the C locus. Intensity causes the phaeomelanin to range in shade from dark red to pale cream.
The eumelanin areas can be affected by the chocolate or pink eye locus.