<https://forums.atariage.com/topic/349547-320-mode-colours-question/page/3/#comment-5270405>
<http://schema.org/text>
"with 320B + 320D: \n \n\n\n\t \n \n\n\n\tthe 320D mode has the advantage of being 1bpp (as 320A) and it can be used (without restrictions regarding pixel placement) for momochromatic sprites / tiles, *only* with color C2 (PO C2 and P4 C2).\n \n\n\n\t \n \n\n\n\tAlso, when you don't have two useful colors in the single 320B palette, you can use the 320D mode for overlapping two sprites and save cycles.\n \n\n\n\t \n \n\n\n\t \n\n\n\t \n \n\n\n\t320D 1bpp can also be used for the star field for which you can use the colors C2 and C3, so for the stars you have 4 colors available from two palettes (320D and 320B share the same PO and P4 palettes).\n \n\n\n\t \n \n\n\n\tIt can also be used to draw explosions, enemy gunfire, etc.\n \n\n\n\t \n \n\n\n\t\n \n\n\n\t \n \n"
<https://forums.atariage.com/topic/349547-320-mode-colours-question/page/3/>