Every colored stat is ranked against the rest of that day's slate and shaded on a continuous scale — deep blue for the best matchups/performances, deep orange/red for the worst, with lighter shades in between. The scale is calculated automatically from that day's data, so it always reflects the current slate rather than a fixed cutoff.
Note: for a few stats (like points allowed or interceptions thrown), a lower raw number is actually the better outcome — those are still colored so blue always means "good for the player/team" and red always means "bad," even though the direction of the underlying number is flipped.