indirect color specification
Computing term for specifying a color indirectly, e.g., via a palette index or reference, rather than by direct RGB values.
This image format uses indirect color specification.
Direct color specification, where colors are given as explicit values (e.g., RGB), as opposed to indirect specification.
Compound of 間接 (indirect) + 色 (color) + 指定 (specification). A technical term likely coined in computing contexts.