make sure it's the only block on the layer, and give the layer transparency
if you cant afford to give up a layer, then you can try and use a block sprite (as in, the block is a custom sprite), and give sprites transparency. with this method, you cant use any sprites that use palettes C-F, because they'll be transparent as well
if you cant afford to do that either, then you're out of luck; there's no real way to give transparency to one object without it being fake transparency aka some form of dithering.
That's not possible. You could, however, use the mode that sets layer 2 as transparent and, if you want a bg, use layer 3.
Originally posted by Ladida
that is, make a checkerboard pattern with the color you want as one color and transparent as the other if you didn't know.