A corollary to the observation that printed conference proceedings are obsolete: it is preferable to use color illustrations than black and white, even for proceedings that will be printed black and white.
To expand a little on the reasoning for this, the audience for your paper consists of three classes of people: those who view it on-screen, those who print it themselves from an on-line version, and those who read the printed proceedings. Color helps convey information more effectively people in the first two classes, the third class is rapidly diminishing, and a careful choice of colors can ensure that even the people who only see the black and white version (or who are color blind) get an understandable figure. So supplying the illustrations in color helps more people than it hurts.
and a careful choice of colors can ensure that even the people who only see the black and white version (or who are color blind) get an understandable figurebut isn't that the hardest part ? there are a number of times I've chosen colors for pictures, only to see them washed out or not as distinctive in black and white. I wonder if there's some nice way of choosing a color map that maximizes disparity even when viewed in grayscale. Sounds like something you might have even written a paper on :)
I like conference proceedings. When a speaker at a conference has hideous math in their presentation, or is otherwise incomprehensible, I have the choice between leaving the room, falling asleep, and poring through the proceedings to try to extract something. It's nice to have the third option. Other than that, though, you're right, they're useless. The same goes for journals.