hi. so, to answer your questions
1. magic actual has no colour, it comes down to a spellcasters intent. black magic typically is magic that does harm, so it should be called negative, white, the oposite. so yes, you can cast black magic and white magic. there's even 'grey' magic, this is magic where it could be considered good or evil. example, you like someone so you cast a love spell on them. while you want to be happy, and want to make them happy, you see it as good since no one's getting hurt, however, you're imposing you will upon another, making it bad.
2. i tend to say look into candle magic. candle magic will help you with focus and knowing colour associations. as you branch out it can help you learn deities, and you could even expariment with oils to try and strangthen certain spells. candle magic is only as strong as the power you put into it, so don't be too afraid of things backfiring and bringing really bad things upon you.
3. if you're interested in elemenal magic, i say go for it. there's nothing wrong with it. start with learning about it though. find out what elements you feel closest with and start with them.
4. astral projection is dificult. so an inexperienced person typically cannot do it. start with meditation, to ap you need to be in a relaxed state, almost as if you're going to fall asleep. once you're able to leave your body, just float around your room. as you progress ease out a bit more, say into the hallway. once you feel ready, think of the astral and you'll be sent there. when you wish to return, think of your room, them your body, otherwise you could be in for a 'bumpy landing' so to speak.
you can mail me if you want further help.