hi amourbliss! i'm a very new knitter so you might want to see what others can offer up but the easiest thing i can think of is to knit the blanket like a tube, in the round. you would knit half of the tube in one colour (e.g. blue) and the other half of the tube in the other colour (e.g. pink!), then sew up each end of the tube and you'd have a double-thick but two sided blanket.
i'm not sure if that would work - what does anyone else think? i know there's also the double-knitting technique which i don't really understand but i think it also allows you to produce different colours on either side of the knitting. perhaps a more seasoned pro can help out here!