As you seem so concerned with the "facts", a more accurate description would be a "hose bomb" as it's made with a garden hose or similar tubing. The effect is more of a firecracker than an actual bomb.
Yeah, also listed in the police press release. Together with green lasers (not listed as missing from the hackspace), pepperspray and some other questionable stuff ...
The full report makes clear that it wasn't the colour that was the problem as such, but the fact that they where stronger than what is allowed to own without permission.