its not a broad generalisation, its the way labs are bread. Working and show, you cannot break a labs temperament up by colour! Or as the Americans like to call it English and American (which is the wrong description btw).
But don't set a Lab apart by colour! I have been around working labs all my life of every colour and there seems to be a generalisation about chocolate labs being mad (btw 'spastic' isn't very PC) is not a good one to make either. I have met mad chocolates and mad yellows. I have never read anything so ridiculous!
I have obviously offended you by stating my opinion which I'm entitled to as are you. As for spastic not being very PC neither is the term "mad". If we are going to be PC we should say very energetic? I have never heard of anyone describing labs as english or american? If you have been around working labs all your life at least you know what you have most don't. Are you a breeder? Do you own all three colors?
Most people and I'm sorry to say (American) breeders do not breed for work or show when it come to labs. They breed for color. They don't know what they have. Breaking them up by color and general descriptions IMO of course is usually the easiest as when it comes to labs. Those are very general terms. There are always exceptions. I've seen black labs that have crazy drive. I've seen some chocolate labs that have no drive.
Generally speaking, in my experience in training and dealing with multiple breeds of dogs, teaching obedience and tracking, and one of my best friends owns a K9 training academy and has for 30 years, I do have an idea of what I am talking about regardless if you like my opinion or not.
I will be one of the few Americans who admit that we tend to definitely mess up breeds. Look what has happened to the GSD's when American began to breed them. Screwed up hips, sloping croups, butts on the ground stance. Sickening.
Please keep in mind, this particular post is opinions and we are all entitled to them.