This is a global style.

Some sites use grey text instead of Black. When you visit these sites enable the script and the text will turn to black & the links to mediumblue.

I recommend to load it both to Stylish & Greasemonkey so you'll have 2 options to use the script.

1- When you visit a new site you quickly enable the userstyle (without reloading the page).
After you leave the site you can turn the style off.

2- Add sites you regularly visit to to the white list of the greasemonkey userscript.