We have to explain better. My opinion is, as mentioned, the Sliver base lends itself to a more control-oriented approach given its flexible abilities that aren't necessarily oriented towards dealing damage like the ones in a Sligh deck. The multi-color mana base just emphasizes this aspect. That's why it's natural to use control-oriented stuff, since you won't be able to race the real aggressive weenie decks unless you blunt the intitial rush and take control of the game. Against slower decks, you get to disrupt key spells while attacking with your hard to kill Slivers. Makes sense to me, but the mana base lets you experiment with anything as long as you take into account the speed limitations of a 5-color weenie deck. Remember that those things like 5-color green and 5-color black could not play as speed weenie decks!