The color of a pill can influence the placebo effect, with blue pills associated with sleep, red pills with stimulants, and yellow pills with antidepressant effects.

“so for some reason most people associate the color blue with sleep whereas or I should say by contrast if people are given a blue a red or a yellow pill and they are told it's a stimulant the subjects taking the red pill here I mean the actual literal red pill I'm not talking about any kind of cultural red pill I haven't seen The Matrix yet people tell me I need to see it but I'm not talking about taking the red pill quote unquote I'm talking about taking a pill that is the color red in an experiment the people that take that pill experience a greater Placebo induced stimulant effect as opposed to when subjects take a blue or a yellow pill for some reason the color red is associated with a quote unquote upper effect or stimulant effect moreover if subjects are given a blue a red or a yellow pill and they are told that the pill will have an anti- depressant effect the subjects that took the yellow Placebo get the biggest anti-depressant effect”