It is a great irony of life that so many things named "Permanent" are just the opposite. This color has moderate to inadequate lightfastness and may fade to a 5 in tints depending on the supplier. Surprisingly, it is found in three oil paints by major paintmakers.
Monona Rossol writes that this may cause methemoglobinemia and has more warnings about it in her writing on pigments which also apply to other forms of PR48 as well.
PR48:2 and PR48:3, which are variants of this pigment, fade terribly to ASTM V (the lowest and poorest lightfastness rating) in gouache.
