'color-forming' originates from Modern English, specifically formed by compounding the noun 'color' (from Latin 'color') and the present participle 'forming' (from Latin 'formare'), where 'color' meant 'hue' and 'formare' meant 'to form'.

'color' entered English via Old French 'colour' from Latin 'color'; 'form' comes from Latin 'forma' (via Old French/Middle English). These elements were combined in Modern English into the compound adjective 'color-forming'.

Initially it meant 'forming or producing color' in a literal sense; over time the phrase retained that basic sense and acquired specialized technical use (for example, describing chromogenic reactions or reagents in chemistry).