These Bulgarian smoke grenades exist in 4 different colours.
White, Orange, Red and Black smoke.
All specifications below came from the manufacterers website : http://www.arsenal-bg.com

Smoke Hand Grenades GH SMK-W(white smoke),GH SMK-O(orange smoke),GH SMK-R(red smoke), GH SMK-B(black smoke) are used:
• for communication and for signaling of territories and sites;
• for creation of smoke-screen (cloud) and temporary cover of materiel and personnel;
• for purposeful diversion;
• for performance of special combat operations.

Operation:
1. Grenade is held in the hand and the lever is held pressed to the grenade body
2. Safety pin is pulled out by pulling the ring
3. Grenade is thrown at the target and after a delay of 1.5 seconds smoke creation starts