Like in the printing of stationery, each colour although Pantone-accurate, may produce different results in application in different media i.e red may appear in two different shades on different papers, on screen, etc.
With that in mind, hermes pigments/dyes produce different results with each skin.
1st. Pic. Havane on chevre.
2nd Pic. Havane on evergrain.
Essentially, they are the same colour - just a slight tonal difference. On chevre it's a brown with a hint of purple. On Evergrain, it's a bit more maroon in comparison.