The AI picking colors for Shelter, for example, was every color but red against 6 mountains on board (was playing vs. a creatureless burn deck). It does fine if it's trying to protect a creature from a concrete threat or make it unblockable by creatures on board. It picked strange and wrong things vs. mono color decks. I'd go so far as to say that the AI could freely look through the opponents deck in secret to determine which color to pick in these situations.

In case of Shifting Sky, the opposite, it should look through it's own deck. A Shifting Sky or Painter's Servant deck will generally pick a color it's deck is built to hose regardless of what the opponents is playing, so if it has Protection from Black in it's deck the correct choice is obviously black and never anything else - this is important because strange things can happen if one is on the board and the AI plays another one and picks a different color. Any light tweak of a deck modeled after the original Paladin will likely prefer Shifting Sky to Mind Bend, so it's kind of important the AI doesn't mess it up.