blue - of the color intermediate between green and violet; having a color similar to that of a clear unclouded sky; "October's bright blue weather"- Helen Hunt Jackson; "a blue flame"; "blue haze of tobacco smoke" blueish, bluish chromatic - being or having or characterized by hue 2....
However you risk “sympathetic detonation” if the main charge in the devices has become “unstable”. Thus a more modern aproach is to use a “low entropy hump” solution of an intense flame that burns through the device or causes the case to split. This is generally a lot lot safe...