Hello Thanks for query . You have undergne surgery for hernia repair 6 months back and noticed your semen to be of dark colour since 2 days .which you have doubt to be related to hernia surgery . Please note that this is not due to hernia surgery but most likely to be due infection of Prostate (Prostatitis) Consult qualified Urologist for clinical examination and get following basic tests done to confirm the diagnosis. 1) Urine routine and culture. 2) Ultrasound scanning of abdomen and pelvis 3) Semen examination and semen culture It should get cured with antibiotics like Doxicycline along with anti inflammatory medication like Diclofenac for 2 weeks . Further specific treatment if required will depend upon result of these tests and final diagnosis. Dr.Patil.