@main: Yellow or white.

[razoredge]

Change main chat color
1. Find these lines:

/*===================================
* Main chat [LuzZza]
* Usage: @main <on|off|message>
*-----------------------------------
*/
int atcommand_main(
const int fd, struct map_session_data* sd,
const char* command, const char* message)
{2. Scroll down until you can see this:

sprintf(atcmd_output, msg_txt(386), sd->status.name, message);
// I use 0xFE000000 color for signalizing that this message is
// main chat message. 0xFE000000 is invalid color, same using
// 0xFF000000 for simple (not colored) GM messages. [LuzZza]
intif_announce(atcmd_output, strlen(atcmd_output) + 1, 0xFF000000, 0);3. Change the 0xFF000000 to any color you want, below are a few color example:

0x00FF00 = green
0xBA55D3 = purple
0xFF6347 = orange
0x70DBDB = cyan

is this what you need?