Why might the colour of my semen change?
Before we get to the question of colour, what exactly is semen? We know it’s the stuff that’s ejaculated from the penis during orgasm, and that it contains sperm – the cells that are made in the testes), one of which might find its way to an ovum (egg), resulting in conception.
Semen is more than just sperm. About 90% of what we ejaculate is fluid made and secreted by the ‘accessory organs’ of the reproductive tract (the seminal vesicles, prostate and Cowper’s gland). When we ejaculate, sperm move from where they’re waiting in the epidydimis (the long, coiled tubes that behind and above each testis), through the vas deferens, ejaculatory duct and urethra (the tube that runs from your bladder to the end of the penis), passing the accessory organs and mixing with the fluids they make, along the way.
When it's ejaculated, semen is a ‘semi-solid coagulated mass’. Within a few minutes it starts to liquefy, to allow the sperm to move around. So if you’re looking at fresh semen, it’ll appear different than if you’re looking at semen that’s been sitting around for a while (perhaps in a container on a lab bench waiting to be analysed, or from a condom).
Everyone’s semen is different and your semen is different each time you ejaculate, depending upon how long since your last orgasm, your state of health and the things you’ve been putting into your body.
Usually, semen is a white or light grey colour, or it might be a pale yellow.
The WHO says yellow semen can be caused by certain vitamins and drugs, or accompany jaundice (when the whites of the eyes and skin take on a yellow tinge, because of a buildup of bilirubin; you can look that up for yourself). The internet says that frequent ejaculation results in whiter semen, and infrequent ejaculation makes it yellow (it’s possible; you could do the experiment yourself to find out).
A few websites say that semen can appear green as a consequence infection. I’d never heard of that until today and there are no reputable sources cited as the basis for those statements.
Semen that is pink, red or brown probably has some blood in it (called haematospermia). (Some places on the internet say eating beetroot can colour your sperm; again, some self-experimenting could provide evidence one way or the other).
Blood in semen is probably quite common (but we don’t know because most men probably don’t take any notice or might not say if they did). The blood can come from anywhere along the urogenital tract. The cause could be inflammation, caused by infection or injury. Haematospermia sometimes occurs when there’s been a long time between ejaculations.
Usually, haematospermia is nothing to worry about. There’s often no other signs or symptoms of any problem, and it goes away fairly quickly on its own. If you notice blood in your semen, it’s not a bad idea to see your doctor. They probably will recommend you keep an eye on it and go back to see them if it persists or returns.