Spy Vs. Spy turned Cold War espionage into a bloody laugh riot, with two shady fellows indistinguishable from one another doing whatever it takes to kill each other for the sake of their team.
The comic that appeared in MAD magazine was presented in black and white because MAD was printed in black and white, plus there's a black spy and a white spy so it just makes sense.
The MADtv cartoon was rendered in B&W to pay homage to the mag but also because war seems so black and white when you're invested in your home team's cause, making it easy for the spies to justify being bomb happy.