I've looked at every openly available piece of PC-98 documentation, and there
don't seem to be any official names for the individual planes. The closest
thing I could find was the description at
http://island.geocities.jp/cklouch/column/pc98bas/pc98disphw2.htm
explaining that they represent the blue, red, green, and brightness component
when using the default PC-98 palette. However, these planes correspond to
nothing else but the 4 individual bits of the final index into the color
palette, and you can assign any color to every single palette slot. Therefore,
it's merely a convention that your own palettes don't have to follow (and in
Touhou, they don't).
Nevertheless, there doesn't seem to be an alternative, and the Neko Project II
source code uses the same B/R/G/E convention, so I'll go with that as well.
Yup, packfiles finally proved that we really have a different set of changes
to master.lib in every game. Also, there are bound to be more of these game-
specific small changes to otherwise identical code in ZUN's own code.
And hey, no need to define that value in the build scripts anymore.
(I've also considered just copying modified versions into the individual game
subdirectories, but it's not too nice to expect people to diff them in order
to actually understand why these copies exist and where the changes actually
are.)
nmlgc