Thanks! Hmm, I guess I know what you mean, Ryu, though the white would probably work better with the lighter version of the palette, i.e.:
. . . but I'm not sure if this is what I've intended. I might tweak the latest version a bit more, together with some minor cosmetic improvements. Tomorrow.
Edit: Here's the light palette version of the recent step of mine:
While run from the .prg, it doesn't make difference -- since Commodore has a fixed, build-in palette, but as for the preview purposes, it might be even a better variant.