The system gives more positive points than negative, all else being equal. And then further, the amount of rep you get is dependent on how much rep the person repping you has.
But practically everyone who has joined since I have been here has started off with a full red bar which slowly shrank and turned toward green with continued posting. It's pretty much guaranteed, just because of the way the system is built.
It's not trouble, though. It's just a popularity contest, in essence. And obviously, until you have a full green bar, you are a terrible ****ing person and everyone hates your guts forever, because rep is the cornerstone of the social flow of KR