Simply put - Spells. Witches perform spells, such as the one described above. Scents, colors, textures, etc. are specific to certain Gods, Goddesses, and Spirit Guides. This will also help to create the desired effect in the Witch. No, not really.
Witchcraft is a very positive, happy belief structure.
It is written directly in our code to harm no one. Unlike Christianity, we have no Satan. There is absolutely no purely negative creature in our beliefs. There is nothing that our ancestors have done to require us to request for forgiveness. We accept just about anyone into our belief structure.