Previously I wrote:
A stateful method, though which might be useful for plain text streams in some applications, would be to encode as characters some of the glyphs for indicating colours and the digit characters to go with them from page 5 and from page 3 of the following publication.
http://www.users.globalnet.co.uk/~ngo/locse027.pdf
Thinking about this further, for this application copies of the glyphs could be redesigned so as to be square and could be emoji-style and the meanings of the characters specifying which colour component is to be set could be changed so that they refer to the number previously entered using one or more of the special digit characters. Thus the setting of colour components could be done in the same reverse notation way that the FORTH computer language works. Yet although the colour components thus set would be stateful until changed there would be no Escape sequence and if an application did not support interpretation of the characters as setting colours, they would just be displayed as glyphs, each either as a particular glyph or as a .notdef glyph.
William Overington Saturday 9 February 2019
