Thank you for your question regarding your testicular symptoms. I am sorry to hear that you are seeing a change in the color of your testicle, which certainly sounds alarming. It is difficult to guess what might be going on without being able to perform a thorough physical examination and ask you questions about your medical history and events leading up to this. For this reason, I encourage you to visit your primary care physician
who will be able to do these things. That being said, I would be curious whether you are experiencing any pain in the testicle. One cause for concern with a purple testicle would be testicular torsion. This usually presents with sudden excruciating pain when the spermatic cord twists around itself and causes a loss of blood flow to the testicle. Testicular torsion is a medical emergency and requires surgical intervention to prevent from losing the testicle. Orchitis, or inflammation of the testicle, can also sometimes cause a change in the color of the testicle. Orchitis can be caused by infection, such as by bacteria that can cause UTIs or by STDs such as Chlamydia. Symptoms of orchitis can be similar to torsion, with pain and swelling of the testicle. If may also be possible that you are experiencing some bruising of the testicle, perhaps after some minor trauma to the area. Please see your primary care physician who can better determine what might be the cause of your symptoms.