Welcome to Just Answer and thanks for your question. Semen is normally translucent to white. How opaque it is often relates to how often the man has had sex either through intercourse or masturbation. If it has been a while, the semen is thicker and more white. The amount and color is also affected by hydration status and foods. You can get some interesting colors if you drink enough KoolAid.
Actually, there are a few things you can do. First is to plan your masturbation and intercourse. Each ejaculation diminishes the sperm count for 24-48 hours. Next would be to stop smoking and using alcohol. Maintain healthy nutrition and exercise. Wear loose fitting shorts and jeans (this isn't the time for the tighty-whities) and avoid hot baths, saunas, and hot tubs. The cooler the scrotum the healthier the sperm. Reducing stress can also help. Good luck!