This is not a new face-feature, it's just a drawn onto the skin texture of the face, so the color won't change sorry.
I made this just for myself because I thought other mods that worked on this face looked too realistic and it just wasn't for me so I drew this more stylized version that is 100% specific to my character so I can't imagine anyone else was looking for poorly maintained stubble.
If anyone's interested I might upload a link to download the .psd of the base-texture file I drew the hair on so you can change the color yourself but it does seem like a hassle.
if theres demand for it i can try and port this to other faces, or if i have the .psd up for download you can take a shot at it urself, i dont mind just give me credit if anyone asks (not a single instance i can imagine where ppl would ask)
also the text on the preview image says pathetic stubble i made it small on purpose but now i cant read it.