'dark-colored' originates from modern English as a compound of 'dark' and 'colored'; 'dark' traces to Old English 'deorc' and 'colored' comes from Latin 'color' through Old French and Middle English.

'dark' changed from Old English 'deorc' to Middle English forms such as 'derk' and eventually to modern English 'dark'; 'color' (Old French 'color', from Latin 'color') entered Middle English as 'colour' and developed into modern 'color' (US) / 'colour' (UK); the compound 'dark-colored' is a straightforward modern joining of these elements.

Initially, 'dark' primarily meant 'without light' or 'obscure' and 'color/colour' meant 'hue'; together the compound came to mean 'having a hue that is deep or lacking lightness', which is the current meaning.