What is intermingling of red and black hair called in cavies?

The intermingling of red and black hair in cavies is referred to as "brindle." This term specifically describes a coat pattern characterized by a mix of two or more colors, where the colors are combined in a way that creates a streaked appearance. Brindle patterns can exhibit varying degrees of color distribution, and the combination of red and black is a classic representation of this type.

Other options such as agouti refer to a different coat coloration pattern that features bands of color on each hair shaft rather than a mixture of two solid colors. Bleeding typically describes a fault in the coat that results in unwanted color melds but does not represent a recognized color pattern. Solid simply denotes a cavy with a uniform color throughout without the mixing of shades, which is different from the bicolor feature seen in brindle. Thus, brindle is the correct terminology for the intermingling of red and black hair in cavies.