I like the idea of a pop of colour against a monochrome background - could do a whole monochrome blanket with some random colours (either the same or a rainbow of colours). Color 'n Cream Crochet and Dream: Tutorial Flower Square V
Illusion Blanket, general instructions by Trish Smith (no specific written pattern). A very clever idea using corner-to-corner diagonal box stitch, with 4 panels joined as they are made. Color graph available on Ravelry page.