So what we read on the topic is to use (as base color) the gray which is
perceptually half-way between black and white. Unfortunately it can mean
different colors. For instance if using the sRGB TRC, the #808080 color is
sometimes cited.
Instead I went with the color LCH (50, 0, 0), i.e. with half perceptual
lightness in "CIE LCH(ab) float" babl space, i.e. #777777 in sRGB. It
corresponds to the 18.42% gray which is often refered to, so it seemed a fine
choice.
This replaces proposal in !683 because the contributor is not responding
anymore, and also it uses the common theme base CSS files used by all other
official themes.
These are not working anymore since we now need CSS themes.
Also we'll prefer to use theme variants anyway.
I also remove a remnant of the old "Small" theme, which was not
installed anymore anyway, and is not useful anymore.
... the python console.
It was using "selected text", which is most often inverted color (close
if not identical to the background color). As a consequence, it made
stdout output unreadable by default, forcing themes to always define a
style for the python console. Using "normal text" is a much better
choice to default to something readable from a parent style.
As a consequence, I also removed "python-fu-console" styling from the
System theme, where there should be as few theming as possible.
I mostly copy-pasted from Dark and Light theme which already had this
style set since previous commit. If anyone wants to finetune colors, be
my guest!
Michael Natterer