lack of nutrition
Smoking can cause a yellow mustache due to the tar and nicotine in cigarettes staining facial hair. It can also slow down hair growth and make the mustache appear dull and unhealthy.
He used wax.
No doubt. You didn't say what color his mustache was originally, but many men's staches become yellowish with age, and there are certainly other causes as well.
They probably can't turn yellow, but some of them are naturally yellow..........
why does wheat turn yellow when it grows in the dark
His hair is brownish black and looks a little greasy.
Cucumbers turn yellow due to overripening, lack of nutrients, or disease.
Fire
Pickels do not grow a mustache -.-
can you use what on your mustache
Latex gloves sometimes turn yellow because of your hands. The oils and fatty acids on your hands breaks down the latex and can turn the gloves yellow.
If you have a wii charger, yes, it does turn yellow