TFA specifically says that the colors added to greys and primary are there to convey states: warnings, destructive operations, tendencies and so on. > They are

TFA specifically says that the colors added to greys and primary are there to convey states: warnings, destructive operations, tendencies and so on. > They are almost imperceptible on my screen, but I would say that the page would look even better if the thin separator was black, and there were no different background shades. Most would disagree. Separating the content from sidebar and asides such as the table of contents is useful because your eyes can follow where you are.