Getting Back To Normal: Let's Talk About Yarn Now

I hope to finish the vest soon (Mr. Isbell has more weekend commitments and I have Brideshead Revisted), which means I'm going to need another project lined up. Continuing the "wearability" theme, I've decided it's going to be a plain pullover crewneck sweater--no fancy cut, no shaping, no stitch patterns.

I know the yarn should be from the magic Montana ranch but I can't decide on the color. I had been thinking navy for wearability, but now I'm tempted by sky blue. A navy blue sweater would be pretty and wearable, but I know that a sky blue one is going to make me happier, getting dressed in the dark cold dead of winter. It just isn't as versatile. Which one should I pick? (And thank goodness this is the my only problem right now, too; not how to get Mr. Isbell a passport and get him, Toby, and myself to Canada.)