Painter's Servant makes all cards the color of your choice. Mycosynth Lattice makes all cards colorless. What happens if they're both in play at the same time? Does the most recently played one take precedent?
The most recently played one takes precidence:
From the rulings on painter's servent:
5/1/2008 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.
5/1/2008 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.
In general continuous effects are applied in time stamp order (rule 613. Interaction of Continuous Effects). More info here: http://wizards.custhelp.com/app/answers/detail/a_id/1030