I have noticed that witth Mac OS 7.5.5 or 7.6.1 it seems to remember the settings and apply them during startup even if the battery is dead (ie the "Welcome to Mac OS" screen is in black and white, but when it changes to "Starting up..." it is in colour). I'm assuming yours has an older OS (7.0/7.1) on it and so that is why you are getting this issue.