'deep-colored' is a Modern English compound formed from the adjective 'deep' and the noun 'color' (US) / 'colour' (UK). 'deep' comes from Old English 'deop' and 'color' comes ultimately from Latin 'color' via Old French 'colour'.

'deep' originates from Old English 'deop' (meaning 'profound, extending far down'), and 'color' comes from Latin 'color' via Old French 'colour'; the two elements were combined in Modern English to form the descriptive compound 'deep-colored'.

Originally 'deep' primarily described physical depth ('extending far down'); over time it gained a secondary sense of intensity or degree (as in 'deep color'), so the compound came to mean 'intensely or richly colored.'