For the advert
in configs/server.ini:
ulx addCsayAdvert "You're playing on %hostname%, enjoy your stay!" 100 255 200 300 10
Put your message in the quotes. The first 3 numbers are the red, green, and blue color values (out of 255). The fourth is the time it waits to repeat (seconds), and the fifth is how long it should stay visible (seconds).
For the @@@.
In ulx/util.lua:
in function ulx.cc_csay (~line 189)
ULib.csay( 0, args )
add your additional color arguments to that call.
ex for red it would be
ULib.csay( 0, args, 255, 0, 0 )