Voila! My first colorwork sweater! I am so pleased with how it turned out. Here's a closeup of the color work. The yarn for the pattern is a slightly different weight from the background, so there are a few puckers and overall tension problems, but they're not so bad that I wanted to start over. And Atty couldn't care less, so we're calling it good.
I had to reknit the body and sleeves after I discovered that I couldn't get anymore of the yarn I'd purchased, even though the lady at the store said that they were getting more and that the dye lots were pretty consistent. Apparently she doesn't do the ordering and has no idea what she's talking about. So I went to a different store and bought yarn that I liked so much better anyway, and bought enough to actually finish the sweater. Lesson learned. Now I'm looking for a cute vest pattern for the first set of yarn.The pattern is officially size 4T, so it's a bit big on him now. The hope is that he'll get more than one season out of it.
Overall, I've decided that knitting with two colors isn't all that bad. The trickiest parts were the two rows where I was trying to hold three colors in my hands and keep all the floats tacked in place and not getting tangled. Yikes. But it was only two rows, so we survived.