Description copied from FM 23-30-1944 :

This grenade is larger than the usual chemical grenade, being about 3 inches by 5½ inches.
It uses igniting fuze M200A1 or M200A2. This grenade can be employed as a signaling device; it is exceptionally visible against a snow background. Three metal flaps at the top should be bent upward to serve as additional bases so that the grenade will not sink below the surface when placed upon snow, mud, or swampy ground. After an approximate 2-second delay, the smoke mixture ignites and burns for about 2 minutes and 20 seconds.

Data from TGRM vol.1 :

Length: 139mm , diameter: 76mm , weight: 794gram.
Blue/Grey body with yellow markings.