There are various synonyms in English language that can be used instead of the phrase "rich in colour". Some of these synonyms include vibrant, vivid, intense, bold, brilliant, lustrous, and radiant. Each of these words has a slightly different connotation, but all convey the idea of a strong, powerful, and visually striking colour. When you describe an object or a scene as "vibrant", you suggest that its colours are lively and dynamic. "Intense" can mean that the colours are deep and significant, while "bold" may connote a daring and audacious use of colour. All of these synonyms can help you to express the richness of colour in a more unique and descriptive way.