Shades of gray at the top of the axis to black at the bottom of the axis. At right is displayed the web color "Gainsboro" "Gainsboro" is a pale tone of gray. Prior to standardization as a web color, "Gainsboro" was included as one of the X11 color names. It was, however, absent from the original 1987 version of the list, but present in Paul Raveling's version which added, amongst other things, "[l]ight and off-white colors, copied from several Sinclair Paints color samples". At right is displayed the web color "light gray" Displayed at right is the web color "silver" This color is
Pale crag martin often treated as the small, pale northern subspecies of the rock martin, but it is now usually considered to be a separate species. The changes in size and colour are continuous, so the evidence for separate species is not strong, although some rock martins can weigh more than twice as much as the smallest subspecies of the pale crag martin. The average weight for "P. o. fusciventris" is 22.4 g (0.79 oz) against 10 g (0.35 oz) for "P. o. obsoleta". There do not appear to be any intermediate forms where pale crag martins and rock martin populations breed close