Brown or brownish colored semen in men can be caused by a variety of reasons. Most often it is caused from blood; "Blood in the semen is very common. It's usually benign.." (Bruce H. Blank, M.D.). That is the good news for men who discover something odd about the coloration of their semen but this doesn't mean that the discovery should be taken lightly.
The first thought by men who notice they have discolored semen is cancer but the fact is, the discoloration can also be caused by an infection, other prostate disorders, and sometimes the cause is never found. Often times especially in younger men, the problem disappears within a few weeks. It is important though that men who do have discolored semen to visit their doctor to rule out any serious illness or disease.
If you suspect that blood is the cause of the problem, you should not take any aspirin products until cleared with your doctor. Aspirin is a known blood thinner and can prevent clotting of the blood. A visit with the doctor may or may not include a physical exam but more than likely, you will need tested for an infection. If this is the cause, this can be treated with simple antibiotics. When a cause of discolored semen cannot be pinpointed, antibiotics are sometimes prescribed as a precautionary measure.
Being probed by your doctor is decided on a case by case basis. You may need your prostate examined or have a cystoscopy performed. A cystoscopy is an examination of the bladder and urethra that can help determine if polyps or tumors are present. This procedure is also often done when blood is discovered in the urine.
Having discolored semen is not as uncommon as it may sound and if you are young and healthy, it's not a condition to become overly troubled. An injury to the testicles or even riding a bike can cause an injury that leads to bleeding that later becomes apparent in your semen. What you should not do however is ignore the problem and pretend it does not exist especially if you are older in age and/or have a past history of health conditions.
Brownish or rust colored semen is typically not a problem that men want to discuss with anyone including a doctor. However, it is vital that men seek professional care especially if the discoloration continues longer than two weeks, is accompanied by pain, or if you over the age of 50.