All domestic chickens have some grey jungle fowl blood, and most probably have some green jungle fowl blood as well. The grey is where yellow shanks and the silver coloration come from. That's been recently proven. The green jungle fowl feature prominently in the ancestry of all the longtails, long crowers, and to some extent the various Asian game breeds. There are people I trust who have done work crossing the various jungle fowl, and the evidence points to heavy doses of green JF blood in all the long tails, long crowers, etc. The Cubalayas have far more green JF blood than a typical domestic chicken, but less than a true long tail or long crower. I don't think the Cubalayas have all that much Grey JF blood, no more than any other domestic breed, and, in my opinion, probably less.