No, this is physically not possible with the kind of laser sytsems we use in showlaser technology nowadays.
Every color spectrum is deflected in a different way, so if you have a multi color input, you get the colors split up as well. That's why it is physically not possible to generate a white star effect with the use of a deflection grating.
Simple grating effects are used in the very common Star Effect Lasers (like the EL-100 MICRO), but also in professional systems like the TARM Beamtable.
Grating effects can also be used with mirrors (BURST-10, LIN-10) and give multi-star effects.
It is possible to have a RGB star effect (like the CS-800S), but its physically not possible to do white.