Playing with the "man" part:
* Colorless-span: This works if you're referring to a man's lifespan, suggesting a life devoid of color or excitement.
* Colorless-plan: This implies a plan or scheme that lacks any vibrant or interesting elements.
* Colorless-clan: This could refer to a group of people who are all uninspired or lack individuality.
Focusing on the "colorless" part:
* Odorless-chan: This is a playful and nonsensical rhyme, using "chan" as a Japanese honorific to add a whimsical touch.
* Tasteless-fan: This could suggest a fan who is uninspired by or indifferent to something.
Ultimately, the best rhyming word pair depends on the context and the specific meaning you want to convey.
Do you have a particular idea in mind for what you'd like the rhyming word pair to express? This could help us find a more fitting match.