How can I change the background colour of a single emacs buffer?

Solution 1:

I've created a emacs lisp package for this: https://github.com/vic/color-theme-buffer-local it uses Emacs' Face remapping to install theme faces locally.

(require 'color-theme-buffer-local)
(add-hook 'java-mode-hook (lambda nil (color-theme-buffer-local 'color-theme-robin-hood (current-buffer)) ))

Solution 2:

You can't.

The background color is generally frame-specific.

You can set the background color of the default face to be frame specific using set-face-background, like so:

(set-face-background 'default "#CCCCCC" (window-frame (frame-selected-window))

Frame customizations are generally controlled through frame parameters. Now, if you look closely at the background-color for frame parameters, you'll see that the default background color is taken from the default face - which is why the above elisp has an effect.

Past that, it seems the closes you can come to a buffer background color is by using the minor-mode buffer-face-mode (added in 23.1) - however that only changes the background for the text of a buffer, and not the entire background.