You may exile a red card from your hand rather than pay Pyrokinesis's mana cost.
Pyrokinesis deals 4 damage divided as you choose among any number of target creatures.
6/8/2016 The number of targets must be at least one and at most four. Each target must be assigned at least 1 damage.
6/8/2016 You divide the damage as you cast Pyrokinesis, not as it resolves. If any of the targets become illegal, damage is dealt to the other targets as originally assigned. If all targets are illegal, Pyrokinesis is countered.
6/8/2016 If another effect causes Pyrokinesis to cost more, you must pay that additional cost even if you pay its alternative cost.