The opaqueness is the sperm (mostly). Guys who have a lower sperm count or who have had a vasectomy will have clearer sperm (as well as those having LOTS of sex. You don't run out of sperm, you just have less per shot).

Whitish is fine. The clear aspect comes from fructose and other secretions the vas deferens makes to enable the sperm to make their journey.

Diet, age, health and other factors change consistency and characteristics of sperm. Yellow isn't really a good color. I mean, whitish yellow is one thing, YELLOW is another. That could be signs of an infection and you should make sure your prostate is doing well, among other things.

Most of all, just take note of any significant changes. Everyone has a different normal. It never hurts to go to a urologist if you have questions or concerns. Hope that helps! less