I tried applying different prefixes to ASCII art color tags, but apparently only <color_colorname> works. I could get other prefixes or background colors to work by adding them after the "color" prefix i. e. <color_light_gray_light_red> or <color_i_red> but they produce errors regarding line length. If I wanted it to work without errors I would have to ask a coder to fix it, but I'm not sure if I even need that. As you said somewhere previously background colors make the art look "blocky" and I did fine without them. So because background colors don't work you shouldn't implement them. Also while we're discussing reducing the file size reduction, BBcode export sets a color for spaces (black), which is unnecessary because spaces look the same no matter the color. It makes the file look a bit messed up because there are tons of unnecessary color tags. And the last step in automation of the export process would be wrapping the lines in " at the beginning and ", at the end. The " at the beginning can be applied in a few seconds using "column mode" or whatever it's called in a text editor, but adiing ", at the end it takes more time because lines usually have different lengths thanks to the color tags. They can be easily added in REXpaint but then they are treated as a part of the image and will be colored. They could be applied automatically before and after each line. ", could also be applied at the point in line where there's nothing but spaces after it and then the spaces would be deleted, but that would probably take more work and the previous solution works fine assuming the user resizes the canvas width to 41 characters, which he should do anyway if he makes art for CDDA. The last line should be without comma at the end, but that would again require a solution with detecting empty space or user resizing the canvas. Honestly it doesn't matter that much, the user could just delete the comma manually. Also I realized the example is kinda misleading, the color tags don't have to be applied every line if the color doesn't change. It could look like this:
"",
"",
"",
" <color_white>╔═══════════════════╗",
" ║ ║",
" ║</color> <color_yellow>╔═ ╔═╔═╗╔═║ ║</color> <color_white>║",
" ║</color> <color_yellow>║═ ┼ ║ ║═║╚╗║═║</color> <color_white>║",
" ║</color> <color_yellow>╚═ ╚═║ ║═╝║ ║</color> <color_white>║",
" ║ ║",
" ║ RIVTECH TRUST ║",
" ║ ║",
" ║ ║",
" ║ 555 993 55221 066 ║",
" ╚═══════════════════╝"