We have no idea where he got that idea, but for weeks he's been talking about a white tree with blue ornaments. Last night, we put it together (three cheers for pre-lit trees, what a BREEZE that was!). Then I put hooks on all the blue ornaments and Zack happily decorated.
Trouble is, he's short, and tended to favor putting all the ornaments on the same branch!
But he was so pleased with the result -- I only helped him a little with the higher branches.
He kept coming back into the room saying, "It's so beautiful!". And that is what Christmas is about.