You can add line to make it only for pacc or require item or anything 
Player say:
Add in 'mods'. Tested on 0.3.6pl1.

Player say:
to get outfit with ID 12, outfit stay after death/logout./outfit demon
Add in 'mods'. Tested on 0.3.6pl1.
XML:
<?xml version="1.0" encoding="UTF-8"?>
<mod name="Outfit change" version="1.0" author="P~" contact="http://otland.net/forum.php" enabled="yes">
<talkaction words="/outfit" event="buffer"><![CDATA[
param = param:lower()
local monsters = {["demon"] = 12, ["frog"] = 226, ["pumpkin"] = 292, ["sheep"] = 13, ["death"] = 300, ["cat"] = 276,
["dog"] = 32, ["dragon"] = 34, ["dragon lord"] = 39, ["elf scout"] = 64, ["deer"] = 31, ["ghost"] = 48}
if(monsters[param] ~= nil) then
local tmp = getCreatureOutfit(cid)
tmp.lookType = monsters[param]
doCreatureChangeOutfit(cid, tmp)
doPlayerSendTextMessage(cid, MESSAGE_STATUS_CONSOLE_BLUE, "Monster use color of your outfit. Change colors and use command again to get other colors.")
else
doPlayerSendTextMessage(cid, MESSAGE_STATUS_CONSOLE_BLUE, "Unknown monster. Use param ( /outfit demon ): demon, frog, pumpkin, sheep, death, cat, dog, dragon, dragon lord, elf scout, deer, ghost")
end
return true
]]></talkaction>
</mod>