The L2 series (with a green shell) is the British version of the M26; it has a 4.4 second fuze.
The L2 was like the early M26 (except it used the L25 series fuze), the L2A1 was like the product-improved M26A1, and the L2A2 was a variant of the L2A1 with a redesigned fuze well for ease of mass production.

The L3 series (with a light blue shell and a black powder filler) is the Practice grenade variant.

The L4 series (with a dark blue shell, non-functional fuze, and no filler) is the inert Drill grenade variant.
The L2 series (with a green shell) is the British version of the M26; it has a 4.4 second fuze. The L2 was like the early M26 (except it used the L25 series fuze), the L2A1 was like the product-improved M26A1, and the L2A2 was a variant of the L2A1 with a redesigned fuze well for ease of mass production. 
The L3 series (with a light blue shell and a black powder filler) is the Practice grenade variant. 
The L4 series (with a dark blue shell, non-functional fuze, and no filler) is the inert Drill grenade variant.
M26 grenade