Concept
Black and Blue is a beatdown deck that plays large under-costed creatures that relentlessly pummel your opponent!

Game Plan
The deck aims to aggressively play under-costed creatures and to apply pressure on the attack from the get go, while essentially ignoring draw-backs of your own creatures. The plan is to win before the draw-backs make a difference anyway.

Creature clashes on the battlefield are normally advantageous with this deck as:

your creatures tend to be bigger than your opponent's, for the same mana value

it's ok to exchange your creatures for your opponent's in combat - as theirs, of the same size, normally cost more to play

you have cheap removal and combat trick spells to turn combat to your favour

Battlefield stalemates though can be troublesome and should be avoided.