A long time ago, I drew up a palette for 256 colors that expands on the standard 16 mIRC colors, and I'll just post it here as a possible suggestion. I'd like to see your opinions on it, positive or negative.
It adds in hexadecimal numbers and is numbered from ^K00 to ^KFF, but the original 16 colors remain in their spots, from ^K00 to ^K09 and from ^K10 to ^K15.
It has no duplicates or spaces left over, and has the following types of colors:
* 16 standard mIRC colors
* 216 6*6*6 RGB cube (aka "web-safe" colors)
* 6 tertiary colors of the rainbow
* 6 darker versions of the tertiary colors
* 12 quaternary colors of the rainbow
* 16 shades of gray
The set of colors was made by first inserting the mIRC colors where they would be if represented as decimal, at 0x00 to 0x09 and 0x10 to 0x15.
6*6*6 RGB colors were calculated and inserted at the end of the set, beginning on 0x28. The duplicate colors in the cube were removed, and replaced with 8 other shades of grays not already in the set.
Tertiary hues were inserted at 0x0A to 0x0F, and darker versions of these were inserted at 0x1A to 0x1F. Orange was replaced with the darker version of yellow at 0x0A, because that did not exist in the mIRC colors. Finally, the quaternary hues were inserted in the remaining spaces, at 0x16 to 0x19 and 0x20 to 0x27.
It's nearly fully compatible with the original ctrl+K colors and takes up the same amount of space, assuming you always used two digits for the colors.
However, it has a few disadvantages. It doesn't have any space for private indices (can get rid of the rainbow colors and shades of grey for that), lacks a transparent color, and a 6x6x6 RGB cube is probably not the best for displaying a large and perceptually uniform range of colors.
Normally I'd prefer a full 24-bit color set for IRC, as that's extremely simple to achieve, except that the IRC protocol has an imposed message length, and it would necessitate a new control code for them.
