Thanks for your query.You have noticed change in colour of your semen to be brownish since 2 days .
Mostly this could be due to infection either in prostate
or seminal vesicle
Please get your semen examination and culture done to rule out infection.
In the mean while Please take broad spectrum antibiotics along with anti inflammatory medication like Diclofenac
twice daily .
Get the prescription of medicines from your family Physician.
Ensure to drink more water.
I think with this treatment it should get cured within a week.