Sometimes, if someone gets turned on (horny) but doesn’t orgasm, it can feel uncomfortable. This can feel like your testicles (balls) are aching, but it doesn’t mean they will turn blue. For some folks, they won’t feel any discomfort at all.
The cure for blue balls is masturbating and ejaculating or just waiting until they will go away on their own. Remember, nagging someone to have sex because you have “blue balls” is not ok and a form of sexual coercion. A person can take care of their “blue balls” themselves.