Bomb Goobs are glowing yellow instead of being blue like regular Goobs. Bomb Goobs are killed in mostly the same way as Goobs, the only difference is that Luigi can not flash them when they are still holding their bombs, they can be only flashed after throwing bombs.
In the game
When Bomb Goobs appear on the fifth floor in ScareScraper, they will hold a bomb which prevents Luigi from flashing them, they will throw the bombs when it's shining red which means it's about to explode, now Luigi can flash them. While Luigi is sucking the Bomb Goobs, they will throw more bombs to attack. They are defeated in the similar way as Goobs.