Can I make the generated HTML page from my DDoc-marked-up D program use richer coloring and type-setting? The default is black-and-white.
I'm currently calling DMD as
dmd -debug -gc -unittest -D -Dd$OUTPUT_DIR
Well, you should probably read through http://dlang.org/ddoc.html to get some of the details, but ultimately, what you need is a css file which tells it how to present the page. That can be set via the DDOC macro.
What I'd suggest doing is taking a look at https://github.com/D-Programming-Language/dlang.org, which contains the code for dlang.org - including the ddoc stuff. In particular, you want to grab std.ddoc along with the css, images, and js folders (as they are all referenced by std.ddoc). If you then give std.ddoc to dmd as part of your documentation build and have those folders in the parent directory of the documentation, the generated documentation should end up looking like the documentation on dlang.org. If you want to put the folders elsewhere, then just tweak the paths to them in std.ddoc.
If you want to change what the documentation looks like, just adjust std.ddoc and the css files accordingly. At that point, it's html and css stuff that you're dealing with, so you'll have to have some clue how those work to make the necessary changes to either the macros in std.ddoc or to the css files themselves. And of course, if you want to do anything with the js files, you'll need to know javascript. You can strip out all of the js and images if you want to. They're just what's used for dlang.org, but again, you'll have to have some clue how html and friends work to know what to do with that. I'm not particularly well versed in any of that, so when I've generated documentation, I've typically made only minimal changes to what dlang.org uses, but all I've typically been looking for is to get more legible colors than the default rather than anything specific.
Sorry that I can't be more specific or helpful than that, but the best that I've done with it is stumble through it enough to get pages looking like dlang.org, since I know next to nothing about web development. Hopefully this will point you in the right direction though.
Something else that you might want to look into is ddox, which uses ddoc comments to generate better looking documentation than dmd does. And it's likely that dlang.org will be switching to using ddox-generated documentation sometime in the relatively near future (some of the details still need to be sorted out, so I don't know when exactly, but that's the current plan). So, using ddox may ultimately end up becoming more common than using dmd to generate the documentation.