This is a 40mm target practice marker riflegrenade.
It uses a bullet-trap system and is filled with a white dye.

The ogive is made of plastic and holds the white dye.
After use, the main parts are reuseable after replacing the ogive.

The grenade is launched by a 5,56mm cartridge which is packed with every new ogive.
This cartridge is deep bronze green.

Information thanks to Marco.