Colouring-matter is a term used to describe substances that are used to impart colour to other materials. The two crossword solutions for this term are DYE and PIGMENT. DYE is a three letter word that refers to a soluble colouring matter that is applied to a material to give it a permanent colour. PIGMENT is a seven letter word that refers to a dry insoluble colouring matter, usually in powder form, that is mixed with a liquid to produce paint or ink.