I have never heard of a "green stripe" that meant anything so can't help you there, but I do have a pair of boots that have the
Greek letter "omega" on them.
According to the website that the link below points too, this means footwear which has soles that provide electric shock resistance.
http://www.ccohs.ca/oshanswers/prevention/ppe/footwear.html#_1_3
