I just ran into a weird issue while tweaking my colour theme for terminal Emacs. The background wasn't appearing as black as expected, but grey, even though the background was set to
#000000. So I opened the 'customize-face' dialog, and then opened the 'choose colour' option for background. This presents the following list:
Notice that the first colour, black, is actually grey, despite being listed as
#000000. Stranger, is there is a second colour named
color-16, with the same code
#000000, and it is full black (see the bottom of the image).
The upshot is if I set a colour to
black, I actually get grey, but if I set the colour to
color-16, I get black.
This doesn't happen in GUI Emacs, where #000000 is called
black, and produces true black. There is no
color-16 in my GUI emacs.
This is a bit awkward as I'd like to have the same color theme for GUI and terminal emacs, but black seems to mean different things. Can anyone explain this?