It would be more natural to use apostrophe + S to show possession. Also, you didn't include any other circumstances besides "when the chips are down", so there's no need for "especially." I would recommend: People's true colors come to light when the chips are down. You might also want to add an adverb of frequency: People's true colors always come to light when the chips are down. People's true colors usually come to light when the chips are down.