I wanted to ask, what is the problem when you...

Causes associated with yellow semen

Urine in the semen
Jaundice
Abnormally high white blood cells
A sexually transmitted infection, such as chlamydia, herpes, or gonorrhea may cause yellow semen. In this instance, a 
Dietary changes: Eating foods that contain dyes can cause yellow semen. The smell of ejaculate may also change if a man eats strong-smelling foods, such as garlic, onions, asparagus, or broccoli
Infrequent ejaculation: If a man has not ejaculated in some time; the semen is more likely to have mixed with urine

Should I see a doctor?

While semen that is light yellow is not usually a cause for concern, there are instances when a man should see a doctor for yellow semen, especially when the semen is a dark yellow
If a man has other symptoms, such as yellowing skin, fever, the semen smells foul, or he experiences pain when ejaculating, he should see his doctor