Brownish / reddish semen color is likely due to blood. Blood in semen or ejaculate is called hematospermia. This can be caused by many conditions. The most common cause of blood in semen is inflammation/infection of the testes, seminal vesicles or prostate gland (prostatitis). A persistent discharge also points to the infection.
A physical examination by a urologist (doctors who will deal it) can give clue of the site of infection or pathology. Digital rectal examination, in which physician, puts a finger in the rectum to palpate prostate can reveal tenderness in prostate or seminal vesicles. A urine culture or semen culture can identify the organisms and their sensitivity towards the antibiotics. This can sometimes be self remitting also, but most of the times an antibiotic course would be required.
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I would be happy to assist you further, if you need any more information.