We have closed a question but the names are shown in different colors. May I know the reason?
Why does Seth have a different color?
As jokerdino♦ says, this is because your browser shows links to pages you've visited (via the exact URL the link uses, that is) in one color, and links to pages you haven't visited (in this way) in another color. (This is not related to cookies though.)
Specifically, the darker-colored usernames are links to profiles you've visited, and the lighter-color username is a link to a profile you have not visited (or you cleared your history/cache since doing so).
There are some factors other than clearing your browser's cache or history that can cause a user's name to be shown light (i.e., as a profile you've not visited). Most significantly, if the user has changed their display name since you last visited their profile, then the link to their profile will be shown light, because changing your display name changes the URL to your profile. (The old URL will still work, but the profile does contain text based directly on the display name.)