@ozzy47 and that would be incorrect. Sure it will change the link colors of user submitted links but it will also change every single link on the site far outside of the use message. The one in your screen shot is a global change where as the one in my screen shot only affects user submitted links in posts.
Use this (add in extra.less and change color etc... to what you like)
CSS:
/* START Link in posts */
.message-userContent a
{
color:#0e0588;
text-decoration:underline;
font-weight:normal;
}
.message-userContent a:hover
{
color:#C30000;
font-weight:normal;
text-decoration:underline;
}
/* END Link in posts */