[Chimera-users] Is it possible to undo an action?

Hi, Is it possible to undo an action in Chimera? I notice that some actions in Chimera can be undid, such as "undo selection" or "undo move". Can every action be undid in Chimera? For example, I colored a selection zone in a different color. But I want to undo this action and recover each atom's previous color. Thank you very much! With best regards, Lesheng