Hello, A yellow-colored ejaculation can cause anyone to get alarmed. Normally, semen is whitish to a light gray in color. It is usually quite thick but tends to liquefy within 20 to 30 minutes. A diet high in sulfur is considered to be one of the likely causes of yellow sperm. Multivitamins are also considered to be a cause of yellow semen. If you haven’t ejaculated for a long time, your first ejaculation after this period of abstinence may also lead to discharge of old semen which may be yellowish in color. Another cause for yellow semen may be the presence of urine. These are normal conditions ,in STDs also one will have yellow semen.