Type "/33change" and a menu will drop down allowing you to choose 12 colors, 3 sizes or turn the particles off.
You can also use voice commands on channel 33, as follows:
/33 on_off /33 small /33 medium /33 big /33 white /33 black /33 gray /33 blue /33 red /33 green /33 yellow /33 cyan /33 magenta /33 lavender /33 rainbow /33 random
Scale: /33 scale VALUE - changes the size of the particles, range 0.03125 - 4.0. (default size is small - 0.5, medium - 1.0, big - 1.8) The command will look like this: '/33 scale 1'
Spread: /33 spread VALUE - changes the time duration of the particles, range 0.1 - 30.0. (default size is small - 3.0, medium - 7.0, big - 15.0) The command will look like this: '/33 spread 7'