While there isn't exactly a concreted color assignment to certain spells, practitioners typically refer to a spell as black or dark if the castor is influencing the will or harming another person. There are some whom refuse to work in any magick that does this as they believe the force will come back 3 fold , while I've never experienced the come back myself it is possible for it to happen. And any evidence I myself have seen of it has been anecdotal and this belief is rooted back in the early 1900's practice called the Gardnerian Wicca.
If you go beyond your limits there can be dire consequences and exhaustion is common due to the high emotional energies needed for manifestation, but I've never heard about anyone dying as a direct result. Any negative consequences are likely due to improper of direction of you lr intentions, so instead of casting towards your intended target the energy remains with the caster or an unintended target, causing whatever maladies to affect them until cleansed. It's important that you maintain precise focus during manifestation, your ritual tools, god/goddess and the ritual itself can assist you in properly setting and maintaining your intention.
For these reasons Black Magick spells can be potentially dangerous for the inexperienced and you should always cast a protection spell and a circle. If something goes wrong take either a salt-water bath, smudge cleanse or shower and clean yourself with a salt scrub while asking your deity for protection against whatever forces you have brought upon yourself.