S: (adj) inert, indifferent, neutral (having only a limited ability to react chemically; chemically inactive) "inert matter"; "an indifferent chemical in a reaction"
S: (adj) neutral (not supporting or favoring either side in a war, dispute, or contest)
S: (adj) neutral (possessing no distinctive quality or characteristics)
W: (adj) colorful [Indirect via colorless] (striking in variety and interest) "a colorful period of history"; "a colorful character"; "colorful language"
W: (adj) colourful [Indirect via colourless] (striking in variety and interest) "a colorful period of history"; "a colorful character"; "colorful language"