This has been out for a while but I couldn't find a thread about it. I've only watched the 89m documentary itself, not the trailers disc but it's pretty good, lots of little details from film historians and new interviews with some of the top directors. https://severin-films.com/shop/all-the-colors-of-giallo-bluray/
Yup, I thought the doc was one of the better ones I've seen, actually felt like I was learning from it rather than just passively watching/enjoying it. It's interesting to see which directors "made it big" by comparing the rooms (presumably in their own house) that they're being interviewed in. The 2 reviews on IMDB seem to like it too : https://www.imdb.com/title/tt9703854/
I'll have to give it a watch sometime soon then. I have the disc, but I've only been watching the trailers. And even then, there's some I avoid because I want to see the movie and giallo trailers can be extremely spoilerish.
That's one of my pet peeves about trailers today as well. Often they have spoilers. It's worse when they come out with a second trailer which give away even more.
Couple of other horror related documentaries on that youtube channel : it's not clear if they actually have permission to host those videos so best watch/download while you can. (To be fair it does say "the films are handpicked and licensed" so maybe it's all legit.)
I'm sure I mentioned this in another thread here, but I got about 10-15 minutes into the All the Colors... doc, saw it was just a bunch of talking heads (I don't remember if there were even any movie clips included) and just said "fuck it" and watched the Giallo trailers on the disc instead.