When i abstain from masturbating for a long time and then masturbate, my semen is watery and not white. but regular masturbation gives white. why?

Concentrated fluid: Semen is a combination of sperm and fluids. Sperm coming from the testicles and fluid from the prostate. While abstaining there is a slight increase in the fluids which causes the semen to be less concentrated. All appears to be normal. Good luck.

Dead sperm: The yellowish/off-white colored semen if one has not ejaculated for a while mean that the semen or ejaculate contains a lot of dead sperm or you may have a small amount of urine in the ejaculate. ( it' s always better to urinate before you ejaculate). This is all good and well if the semen does not have a foul odor as this could mean an infection.