Semen color and consistency can change based on age, diet, and frequency of ejaculation. But given your symptoms, particularly with the fact that you recently had unprotected sex, TeenHealthFX does think that it is important for you to meet with your primary care physician. Normal semen can have an off-white or even yellow-tinted appearance, but if the semen is a very pronounced yellow then it could be due to an infection, such as a urinary infection, prostate infection, or an STD like gonorrhea. Yellow-tinted semen could also have urine in it. It is possible that the rash/itchiness is connected to whatever is causing a change in your semen, but it could also be a completely separate issue, such as an allergic reaction.
FX cannot give you any kind of accurate diagnosis over the web, but we think you should meet with a medical care professional so you can be properly diagnosed and treated – and that you refrain from sexual activity until you do. If you do have an STD, speak to your doctor about the best ways to ensure you do not pass on the STD to others. If you don't have a doctor and live in northern New Jersey, you can call the Adolescent/Young Adult Center for Health at 973-971-6475 for an appointment or contact your local teen health center or Planned Parenthood. You can also contact your insurance company for a list of in-network providers.
FX also wants to make sure you know that abstinence is the best way to prevent the transmission of STDs. And, in general, if you do choose to be sexually active, have yourself and your partner tested for STDs prior to becoming sexually active and use condoms each and every time you have vaginal, anal, and/or oral sex to reduce the likelihood of transmitting any STDs. Again, if you do have any STDs, please check with your doctor about specific methods of reducing transmission depending on the particular STD.