Iridescent Sliver

Sliver creatures you control have, "{t}: Add one mana of any color to your mana pool."'
If either Manaweft Sliver is under your control or Gemhide sliver is out on the battlefield, and whenever a sliver is tapped for mana, each sliver tapped for mana can be tapped for two mana of any color instead.
Eerily shinning through the darkness this sliver lays and waits for its next victim.