When the "Colored usernames" option is enabled in your advanced settings, the following colors are used:

• Most Members, including Unactivated members, basic Members, and Privileged members, use the same steel blue colors used for general tags and all other links on e621; light steel blue when unselected, and a deeper steel blue when a cursor is hovering over it.
• Blocked members have struck through usernames.
• Former Staff have mint usernames.
• Janitors and Moderators have red usernames.
• Admins have orange usernames.

Please note that some themes and userstyles may change these colors.