The colour says what a bar IS, not how it scores: the accent is the one this page is about, grey is everything it is compared with, and the hollow bar is the web overall — the ruler, not a rival. Whether a figure is above or below the rest of the web is in the number and in the arrow beside it.
Every figure here comes from a sample, not from counting every site — so it carries a margin: how much it could move if we had happened to sample different pages. A figure measured on a thousand pages has a wide margin; one measured on a hundred thousand has a narrow one. It matters for one thing: two figures that differ by less than the wider of their margins are not one above the other, they are tied. That is why nothing here has a position number.