How are blue orchids made?

Occasionally a florist or garden center will have vibrant blue moth orchids (Phalaenopsis) for sale.  Blue is not a color that naturally occurs in orchids.  These orchids are typically white flowers dyed to achieve this unique color.  A  food-grade dye (the formulation of which is typically proprietary) is injected into the base of the flower scape (stem).  As water moves up the stem to the opening flowers, the dye is carried with it changing the color of the white bloom to blue.  The bloom will remain that color until it falls off.  Should the orchid rebloom, the new flowers will be their original white color.

Blue isn't the only color orchids are dyed.  Other unnatural colors like orange or bright green are also popular around certain holidays.  You can often identify the orchid as dyed when you see younger flowers further out on the scape that are lighter in color than the more mature blooms that opened first.  Additionally, the injection site can often be found if you carefully inspect the base of the flower scape near the leaves.