Sliver Hatchery

Sliver Hatchery comes into play tapped.
{t}: Add one mana of any color a land you control could produce.
{t}: When a sliver creature enters the battlefield under your control, if it's power or toughness would be 1, proliferate.
(You choose any number of permanents and/or players with counters on them, then give each another counter of a kind already there.)