Because red lights are bad?
https://usatoday.com/story/money/2018/06/25/retailers-testing-blue-lights-drug-users/730073002/A handful of convenience stores and supermarkets are experimenting with an unusual strategy: Installing blue lights in bathrooms in order to quell drug usage by making it more difficult for people to inject themselves. The theory is that drug users, who often use the privacy of bathroom stalls to shoot up heroin and other drugs, would have difficulty finding their veins.
