Magic has no color. Therefore, black and white are really irrelevant in my opinion. The intent of the practitioner determines whether the outcome of a spell or ritual will be positive or negative, beneficial or harmful.
You can practice positively or negatively without fear of achieving a state of non-balance. Magic is a part of nature, and in my experience nature finds a way to balance itself out be it one way or another.
If you search the site there are articles and threads for both of those subjects, so you could try looking through those. There are also books that might help you out. A few good books that I would suggest to get you started are:
The Witch Book: The Encyclopedia of Witchcraft, Wicca, and Neo-Paganism. - Written by Raymond Buckland.
Herb Magic for Beginners: Down-to-Earth Enchantments ~ Written by Ellen Dugan
Those two books above have a mass of information on candles and herbs. Two other good reads are:
Wicca: A Guide for the Solitary Practitioner. ~ Written by Scott Cunningham.
Living Wicca: A Further Guide for the Solitary Practitioner ~ Written by Scott Cunningham.
While these books don't really have information on herbs or candles they can be useful to new practitioners, in my opinion. They have information on the basics and various other useful topics.
If you have any other questions on herbs or candles, let me know. I myself love working with both and have done so for a while.