Technically, Fair Isle is a sub-style of knitted colorwork that includes a specific XOXO-type abstract banded pattern that originated on Fair Isle in Scotland; this book's cover shows a pretty clear example.
The type of colorwork in this piece is not Fair Isle. It's crochet, for one (although you could certainly mimic Fair Isle in crochet), but it's also not a banded pattern nor does it incorporate the XO pattern. This is more like what is called intarsia: a pictoral motif set into a plain background.