Here are a few options, depending on the context and what you're trying to achieve:
* For a humorous effect: You could use a playful rhyme like "colorless fan" or "colorless plan."
* For a more serious tone: You might consider using a word with a similar sound but not a perfect rhyme, like "colorless span" or "colorless than."
Ultimately, the best rhyming word pair depends on the specific situation and the desired effect.