The color mentioned, Prussian blue, has a particular history with regards to Japanese art. Remember that at the time, imports were banned in Japan and thus to even own the color was something of a rarity. Based on the contemporary situation and his own history and interest in Western culture and art, it's pretty likely that Hokusai chose the color deliberately, and not simply that he liked blue "because he wanted it for the waves." Remember that he was nearly 70 years old when he started working on
Thirty-six Views of Mount Fuji. Typically artists at that level of experience don't choose to use rare new materials just for kicks.
Hokusai was one of the first Japanese printmakers to boldly embrace the colour, a decision that would have major implications in the world of art. Using it extensively in his series Thirty Six Views of Mount Fuji (1830), of which the Great Wave was the first, the pigment especially lent itself to expressing both depth in water and distance, crucial atmospheric qualities to render land and seascapes.
Hokusai drew influence from a particular “Rangakusha” (scholar of Dutch texts) painter named Shiba Kokan, who experimented with European principles of composition. In The Great Wave, Hokusai abandoned traditional Japanese isometric view, where motifs were scaled according to importance, and instead adopted the dynamic style of Western perspective featuring intersecting lines of sight.
In short: the work itself incorporates deep influences from European art. Ergo, it's pretty standard art criticism to assume that the choice of materials and colors were also chosen deliberately.
http://theconversation.com/friday-essay-from-the-great-wave-...