On the online seat maps there sometimes is a range of seats that have a blue (actually blue-grey) background. They are seats that I would think are E+, but are shown as E. For example, on a Boeing 737-800 for UA1035 (IAH-UIO) rows 8-15 are white seats with the blue background. Rows 7 and 20 and 21 are blue on a grey background (E+), while everything further back is white on the grey background (normal E seats).

So what does the blue band of seats mean???

Thanks!