Check your state laws. I think the red flares mean Emergency, while either the white or green are for practice. Google search this and see if you can find out. I think it varies by location and the type of flare shot. I have one of the Polish guns with the case and lanyard. Picked this up for around $30 with the case. These, the ones without the trigger guard, are copies of the Russian SP-Sh2 M44 flare pistol used in WWII and later in the Cold War era.
They may still use them in Russia, in fact. Century Arms still has these for sale, and there are several dealers who sell these online as they can be mailed, and bought without a ffl.