Colourfast is a term used to describe the ability of a material or substance to not fade or change colour when exposed to light, heat, water, or other environmental factors. Some possible synonyms for colourfast include fade-resistant, non-fading, washable, durable, permanent, and steadfast. Other related terms might include fastness, colour retention, colour stability, and colour consistency. These terms are often used in the textile, printing, and manufacturing industries to describe products or materials that maintain their original colour over time. Overall, there are many different words that can be used to convey the idea of something being resistant to fading or colour change.