/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'.