Luckily in the blue & red card pool, there are thousands of great options for every spell slot
The Necrons are basically an army of robotic skeleton warriors, so putting them in black and making them artifact creatures makes a lot of sense
Of note, every color except blue is represented in the decks
The most common deckbuilding mistake I come across is people running far too little mana than they should be
Whether this is because it's indestructible or because it will just come right back out of the graveyard, Deglamer can solve the problem by simply shuffling it back into the opponent's library and putting it out of their reach
Before I begin, let me explain that to cover the breadth of the topic I am going to be talking about permanent destruction in the broader sense (meaning, what can each color do to deal with each permanent type) and not specifically how each color "destroys" permanents in the technical sense of the word "destroy," which in Magic has a particular meaning