sweater (like a top-down/bottom up seamless type) and/or hat, preferably with worsted.

If I find separate sweater patterns and fair isle designs I like, if the sweater is top down, do you flip over the fair isle pattern and do it upside down? I suppose some fair isle patterns are symmetrical so it wouldn't make a difference anyway.

Most are symmetrical, but you can just turn the chart over if it's not.

I've had to do that when the body was bottom up and the sleeves were top down.

I haven't done enough fair isle to help you there, but I would think using "boyish" colors would work with most patterns as long as they aren't flowery.