Coloured Characters (was: 0027, 02BC, 2019, or a new character?)

[Richard Wordingham via Unicode]

On Thu, 22 Feb 2018 00:04:34 +0100
Philippe Verdy via Unicode <unicode at unicode.org> wrote:

> On the opposite, colored in Arabic or hieroglyph texts is a a useful
> emphasize and sometimes semantically significant (some rare old
> scripts also used dictinctive colors): we are in a case similar to
> encoded semantic variants for mathematics symbols. But here again
> color cause a severe problem of accessibility and rendering on
> various surfaces (e.g. is the paper/screen white or black ?

In my case, I just used the colours 'foreground' and 'red'.  They work
well on both light and dark backgrounds.  The difference wasn't so
easy to see when the foreground was a different shade of red!

> cannot see the encoded color correctly and it is interpreted
> verbatim, the text will not be readable at all; what is really needed
> is a set of symbolic colors: normal color, color vaiant 1, color
> variant 2, and Unicode can perfectly encode these as combining
> diacritics !)

Heraldry has the same problem when objects are depicted in their
natural colours.  (The colour term then used in English heraldry is
'proper'.)  Microsoft has a scheme of palettes, but the design is that
the application choose the palette from a predefined list. The font can
nominate palettes for light and dark backgrounds; otherwise the
selection protocol is completely up to the application. 'Foreground'
and 'background' are the only externally defined colours. There's no
ability to explicitly choose, say 'text stroked sable and dotted
gules'.  Instead, it's 'text stroked sable and dotted proper', with a
choice of palettes to define 'proper'.

Richard.