1) The bloom of the apple or the blossom of the tree.
In one of the examples noted this was the colour of a tunic, perhaps the ‘florescence thought of as the culminating beauty of the plant’, a definition of ‘bloom’ in the OED: 1341 necnon collobium meum longum coloris de appelblome cum tunica’ ejusdem coloris, York. It was also used of a cloth, presumably named from the colour: 1341 do et lego … sorori meć unam tunicam de appelblome, York. The author of The History of Hemingbrough quoted an example from a will of 1320 which he described as ‘a cloth called appelblome’ and that seems also to be the meaning later: 1392 unam togam de appilblome furratam cum foygnes, Swinton in Ryedale.