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.
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.