Rulings

• 2008-05-01
  Each card becomes a new object as it changes zones, so this effect will apply to it from scratch in the new zone. Zone-change replacement abilities that care about the new color (like "[color] permanents enter the battlefield tapped") won't work because those effects are applied as the card is entering its new zone. Zone-change triggered abilities that care about the new color (like "when a [color] permanent enters the battlefield" or "when you cast a [color] spell") will work because those effects apply after the card is already in its new zone.
• 2008-05-01
  If something affected by Painter's Servant is normally colorless, it will simply be the new color. It won't be both the new color and colorless.
• 2008-05-01
  The effects of multiple Painter's Servants are cumulative.
• 2008-05-01
  This ability affects every card in every game zone, all tokens on the battlefield, and all spell copies on the stack, regardless of who controls or owns them.
• 2008-05-01
  While Painter's Servant is on the battlefield, an effect that changes an object's colors will overwrite Painter's Servant's effect. For example, casting Cerulean Wisps on a creature will turn it blue, regardless of the color chosen for Painter's Servant.
• 2008-05-01
  This ability doesn't overwrite any previous colors. Rather, it adds another color.