The semen of normal people is grayish white or slightly khaki, which is quite viscous. Semen solidifies rapidly after injection, and blood clots generally liquefy naturally within 5 to 20 minutes. If abstinence lasts for a long time, the color will turn yellow because of the changes in physical and chemical properties. This is all normal.
Semen abnormalities include: the semen is milky white or yellow-green, indicating that there is inflammation in the reproductive tract, which is likely to be purulent infection of the prostate and seminal vesicle.
Semen is red, indicating that semen contains red blood cells, which is commonly called "blood essence". Blood essence is mostly caused by seminal vesiculitis or prostatitis. This kind of blood essence caused by inflammation is mostly reddish. If the small blood vessels rupture due to vascular malformation, the blood essence is bright red and blood clots can be seen.