There are plenty of ways to describe "adding colour" that can help add variety and maintain interest in your writing. Some synonyms for "adding colour" include "brightening up," "bringing vibrancy," "injecting interest," "enlivening," "spicing up," "enhancing," "beautifying," "enriching," and "enlivening." Each of these words has its own unique connotation, so choose the synonym that best suits the tone of your writing. By varying your language and using synonyms, you can keep your readers engaged and interested, adding colour to your writing.