Trying to change all the parts color but isn't responded to the "v.Material == "Grass" line?

Heres the script, it's responding to print the part's name but couldn't find the part's material.

for i,v in pairs(game.Workspace:GetChildren()) do
	if v.Name  == "P1" and v:IsA("WedgePart") then
		print(v.Name)
		if v.Material == "Grass" then		-- Not working here
			v.BrickColor = BrickColor.new("Medium green")
		end
		
	end
end