When composing private messages (posting.php), you has to define the recipient(s), user(s) or groups (assuming the board admin enabled the mass private messages and sending to a given users group). Although the color of usernames are displayed, it's not the case of user groups. First inconsistency.
The colors are correctly displayed when you view a private message (ucp_pm_viewmessage.html), but the user color group names are not in bold (font-weight), unlike colored usernames. Second inconsistency.
Same applies to reported private messages, when viewing in the Moderator Control panel (mcp_post.html). Third inconsistency