I used this free pattern on Ravelry. The pattern was written for intarsia, but I hate seaming knits and I hate weaving in ends even more. The finished product probably would've looked a little better, but there was no way I could finish weaving in 50+ ends (per hat!) in a month. So I modified the pattern to be fair isle, which was a different challenge - with such long blocks of color (sometimes 10 stitches) I had to worry about catching the floats on the wrong side. I can see where the floats are caught, and some uneven tension where colors switch in the finished hats. The construction was difficult, and the final product isn't as neat as I'd like, but the kiddos love them. These took surprisingly little yarn - I have enough left for at least one more medium size hat.
I used blue and white Plymouth Yarn Worsted Merino Superwash, and random scraps of black and red worsted wool. The big hat was knit on US6 and US7 needles, and the small hat was on US4 and US5 needles. I plan to make a medium with US5 and US6 for Ethan next winter.