Di che colorazione si tratta?

All 3 have as E-locus E/E.
The first is the sex-linked chocolate (hobbyname)
The second is a mutation on the I-locus and called "dun" but have also as hobbyname chocolate (the autosomale chocolate).
The third is also a mutation of the I-locus and called Khaki (hobbyname)

Conclusion: hobbynames give confusions, genotypes give the exact name.

chocolate : choc/choc = sex-linked mutation on Choc-locus (hens : choc/-).

dun/chocolate : I^d/i+ = (single) mutation on I-locus and autosomale.

Khaki : I^D/I^D = (double) mutation on I-locus and autosomale.


The genotype of the Buff: eWh/eWH Co/Co s+/s+ * s+/- ml+/ml+ Mh/Mh Di/Di
The genotype of the chocolate : E/E s+/s+ * s+/- or S/S * S/- ml+/ml+ mh+/mh+ choc/choc * choc/-

As you can see this is what Tünde said there is NO simularity between Buff and chocolate genotypes.