It's the colour palette. The first one in the first row is the normal colour for text, the second one in the first row is the system colour (ie the colour of descriptive text like GP in the menu) and some of the others might be used for other things like low HP, though I wouldn't know as I've never used 2k. Also, you can use any of them in a regular message with the code: \c[a] where a is a number between 0 and 19 - it will change the colour of message window text to that of the corresponding square. Ie - 0 is the normal one, 1 would be the system colour, 2 would be the next one in that row, 10 would be the first one in the second row, etc...