by Janie — The color blue is an odd­ity. Of all pig­ments in na­ture – chem­i­cals that se­lec­tively ab­sorb and re­flect cer­tain wave­lengths of vis­i­ble light – blue ones are among the rarest. Pro­ducing blue dyes was once such a costly busi­ness that me­dieval Eu­ro­peans consid­ered it to be as pre­cious as gold...