Contrary to popular misconception, good green colours were hard to produce on fabric with dyestuffs. Some dull and pale greens (brownish, greyish, or yellowish coloured) can be produced from plant matter, however the bright green colour of plants is not easily transfered to fabric. (despite all the evidence of grass stains). To get a nice clear green, fabric was first dyed with a yellow dye (eg weld, dyer's greenweed) and then, once dry, overdyed with a blue dye (woad). As such a "good" green fabric might concievably cost more than a blue fabric.