mottle

(noun) an irregular arrangement of patches of color. Example: "It was not dull grey as distance had suggested, but a mottle of khaki and black and olive-green."

(verb) mark with spots or blotches of different color or shades of color as if stained. Synonyms: streak, blotch.

(verb) colour with streaks or blotches of different shades. Synonyms: dapple, cloud.