first, magick has no colour. the intent of the caster will make it positive [white] or negative. [black] magick has a lot of gray area's to it as well, so you need to think before you cast. some people do put colour to a particular type of magick as a type of short hand, but magick is intent, not colour based.
you should work on meditation, chakras, energy work, and circle casting before you try your hand at a spell. these are basics needed to cast a spell correctly. meditation clears the mind and helps you focus on a single task [extremely important to casting a spell successfully] energy is needed to cast a spell, and chakra's will help the flow of energy in your body [though the energy used in spells comes from outside, not your bodies energy] finally circle casting to protect you and create a sacred ground for your spell work.
keep in mind while magick is very powerful, it cannot go against nature. the things you watch in movies, such as flight or transformation, cannot happen with real spiritual magick. spells to protect, calm, or heal will work however. if you do have a spiritual path as well, i suggest studying that first, buy a book on the subject and learn it's views on magick. for example, if you've decided to convert to Wicca, most Wiccans are against spells harming others such as curses, so you can't cast these spells. anyone can cast magick, you don't need to belong to a certain religion, remember that before you make any snap decisions. if you do choose to convert to a new religion, do a year and a day ceremony where you study and soul search before you make your final choice. [also, good luck finding a teaching, i don't take on students, i wanted to point you in a direction is all]