He was stating that glass is sand as far as health is concerned. And glass is literally nothing but sand, no debate about it. And he clearly stated that they will scratch the inside of your injector and noted it as a "negative" to their use.
About the blue flake, I use Canadian blue (I think I'll have to check) in one of my black colors that absolutely kills the fish where I'm at. I use small Canadian blue flake and large silver flake together and it works really really well for me. If you're wanting a bait like almost everybody else has when making black and blue flake then the royal blue I believe is what you're looking for. I will check my flakes tomorrow afternoon when I get up and make sure for ya.