I am 26 years old my semen's color is yellow and it has been for years now so it is not a sudden change. i have no signs of infection no fever no pain i think the reason is it gets mixed with urine when i ejaculate. would that affect fertility?

A slight yellowish color in semen is normal and would not affect fertility. For healthy diet: http://www.choosemyplate.gov/., exercise 30 minutes/day, drink enough water daily so your urine is mostly colorless, have safe sex, no tobacco alcohol weed or street drugs. Get HPV vaccine. Wish you good health! Safe sex: https://www.hopkinsmedicine.org/health/wellness-and-prevention/safer-sex-guideline

Ejaculation and urination do not occur at the same time so it is not from your urine- as it would make the ejaculate watery. It should not affect fertility. You can have your semen examined too.