Chaos Bolt’s tooltip says that it deals Chaos Damage, but this is not true. Demon Hunter’s Chaos Strike deals Chaos Damage but, alas, CB does not.
Chaos Bolt = Fire, Nature, Frost, Shadow, Arcane = NOT Chaos Damage
Chaos Strike = Physical, Holy, Fire, Nature, Frost, Shadow, Arcane = Chaos Damage
Either fix the CB tooltip (Prismatic or Chromatic Damage or w/e) or rename the spell to Prismatic or Chromatic Bolt.