Ok, if you're going to classify magic like that -- which may be a little simplistic -- you have to define your terms. Here are some general definitions that I believe would be fairly commonly accepted:
"White Magic" is an effort to tap into the power of the universe (ie: magic) in order to commune with the divine or achieve a higher state. Baically it's mystical rituals.
"Black Magic" is an effort to tap into universal forces in order to cause harm or to control other people.
"Gray Magic" is an effort to tap into universal forces in order to bring about a specific outcome that you desire, without causing harm or adversely affecting anyone else. .
We could also define "Phantasmal Magic" as the kind of flashy stuff you see on TV and in movies. Don't expect to encounter anything even close to that in real life!
Most people who dabble in magic do spells that can be considered Gray Magic, such as the one you're talking about. Very few actually practice the white or black varieties.
Anyway, if you're concerned about possible unanticipated results from a magical working, consider using some kind of divination technique beforehand (runes, tarot cards, i-ching, etc.). Ask "what might be the result if I did x," and see what the runes (or cards, etc.) tell you. Consider whether you're willing to live with those ramifications. Also consider Karma, or the Wiccan Law of Threes -- bringing "negative" things into the world will probably come back to haunt you in some way.
Don't be afraid to go ahead and try the spell. You'd be surprised how much power you have to manipulate events around you (though typically when things work out as you want them, it seems totally natural).