Paper balls useless, Apples save you from being eaten.
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Those are the only 3 types the color determines the grade and rarity
Red is the most common it saves you from being eaten by Bella and fill her stomach a bit the more stuff she has in her stomach the longer it take for her to digest.
Green is just a better version of the red apple
If bella eats a crazy apple it will make her start vibrating and starts she will burp out stuff in her stomach it could be useful if she swallowed a key you needed.