Caged Sun (CM2) from Commander Anthology Volume II, available at 401 Games Canada.

• Rarity: Rare
• Finish: Normal
• Artist: Scott Chou
• Card Text:
  As Caged Sun enters the battlefield, choose a color.
  Creatures you control of the chosen color get +1/+1.
  Whenever a land's ability causes you to add one or more mana of the chosen color, add one additional mana of that color.