Type "/33change" and a menu will drop down allowing you to choose 12 types, 12 colors or turn the particles off.
You can also use voice commands on channel 33, as follows:
/33 on_off /33 default /33 star1 /33 star2 /33 star3 /33 star4 /33 star5 /33 plasma /33 fire1 /33 fire2 /33 heart /33 rose /33 yingyang /33 white /33 gray /33 black /33 blue /33 red /33 green /33 yellow /33 pink /33 cyan /33 magenta /33 lavender /33 rainbow