/COLOR roster (status wildcard (color|-)|clear)
 /COLOR mucnick nick (color|-)
 /COLOR muc (jid|.|*) [on|preset|off|-]

The 'color' command allows setting dynamic color properties of the screen.

/color roster clear
 Remove all color rules for the roster.  All roster items will get its default color.
/color roster status wildcard color
 Set a color rule (or overwrite, if it already exists).  The status is string containing all statuses the roster item can have for the rule to match, or * if any status is OK.  Wildcard is the file-matching wildcard that will be applied to JID.  Color is the wanted color.
 If color is -, the rule is removed.
 If more than one rule matches, the color from the last created (not overwritten) is used.
/color mucnick nick (color|-)
 Marks the nick to be colored by given color.  If a MUC has colored nicks, this one will be used.  If color is -, the color is marked as chosen automatically, which means it will not be used in 'preset' coloring mode, but will stay the same in 'on' coloring mode.
/color muc (jid|.|*) [on|preset|off|-]
 Sets a MUC nick coloring mode.  If a jid (. means currently selected jid) is provided, the mode will apply to this specific MUC.  If * is used, it will be applied to all MUCs, except the ones set by their jid.
 Mode 'on' colors all nicks, 'preset' only the ones manually set by /color mucnick command and 'off' colors none.  If not specified, defaults to 'on'.  Mode '-' removes the mode from given JID, which means the global one will apply.  You can not remove the global mode.
 Default global coloring mode is 'off'.