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 is milky white or slightly yellowish green, indicating that there is inflammation in the reproductive tract.
It may be a purulent infection of prostate and seminal vesicle. Semen is red, indicating that semen contains red blood cells.
Often called "blood essence". Blood essence is mostly caused by seminal vesiculitis or prostatitis. This blood essence caused by inflammation
Most of them are red. If the small blood vessels rupture due to vascular malformation, the blood essence is bright red and blood clots can be seen.