'tortoiseshell-colored' originates from Modern English, specifically the compound of 'tortoiseshell' and 'colored', where 'tortoiseshell' referred to the decorative shell material of certain turtles and 'colored' meant 'having color'.

'tortoiseshell' developed in English as a compound of 'tortoise' + 'shell' (with 'tortoise' ultimately borrowed via Old French from earlier Germanic/Latin influence), while 'colored' derives from Old French/Latin 'color'; the compound came to be used adjectivally to describe items that have the appearance of tortoiseshell.

Initially it referred literally to the material or hue of actual tortoise (turtle) shells used in ornaments; over time it broadened to describe any object whose color or pattern resembles that material (a descriptive color term).