Complex sentence: In the 18th century Prussian blue became popular, and was particularly prominent in the landscapes of Hokusai and Hiroshige, as was "bokashi", where the printer produced gradations of colour or the blending one one colour into another.
Split into simpler sentences: In the 18th century Prussian blue became popular, and was particularly prominent in the landscapes of Hokusai and Hiroshige. Also prominent in these two artists works was "bokashi", where the printer produced gradations of colour or the blending one one colour into another.