nowofresh, your code doesn't does anything of what he wants O_o, i think you gotta read it again
function onEnterSetColor ( thePlayer, seat, jacked )
local accountname = getAccountName(getPlayerAccount(thePlayer))
if isObjectInACLGroup ( "user." .. accountname, aclGetGroup ( "Admin" )) then
setVehicleColor(source, 0, 0, 0, 0)
setVehicleHeadLightColor(source, 0, 0, 0)
else
setVehicleColor(source, 16, 16 , 16, 16)
setVehicleHeadLightColor(source, 0, 255, 0)
end
end
addEventHandler ( "onVehicleEnter", getRootElement(), onEnterSetColor )
should work, try it (not tested)