It is not a real breed but more of a coloring.
The color matching of the hair can be in two or three colors, mixed up to obtain a mélange tint.
There are many variables of this coloring, not all perfectly fixed.
Eye color variable depending on the background tint.
Cavia Roans Golden - Cavia Roans Chocolate
Guinea Pig Roans Chocolate (photo www.australiancavysanctuary.com)