The blue color screams “inert.”
Bingo.
The blue color also also screams newer fuse on a 1940s or 50s shell. There are idiots out there who would fill a body with blackpowder and screw on the fuse from a legal smoke or illum grenade. Unpredictable results and other merriment are likely.
I wouldn’t expect a home made grenade to be super stable.
But that’s just me.