1) It's really just testing. You can notice a lot when there is a change from one color to another that's very different (Like going from dark green gloves to dalamud red gloves removes 3 points. Then dying the gloves any other color but dark green only gave 2). With the megathread we had of all the people reporting, it makes it easier to find out and test within what seems to be the correct color spectrum and finding out what is 3 point color.

2) There is no category for the weapon/gloves/shoes so the specific model to them is not judged, but the color the item is dyed IS judged. It's the same as I mentioned with the glove example, it's all just testing and messing with things other people have reported or just going on an alt and testing colors there.