Gray.

It had started with the bomb. 

Bruce had spent a large amount of his life interested in physics. He liked how things fell, how they spun on an axis, how they flew into the sky given enough force. He liked the simplicity of it. 

Hide behind mathematics all you like, he would think, all you need to counteract gravity is a bigger force. That’s all physics was, just forces.

He liked how every object in the universe had its own gravitational pull, even a small one. Everything from planets, to meteors, to people. The only reason people weren’t walking around with coins orbiting them was because the Earth had a bigger force of gravity.

But even the Earth’s gravity could be counteracted, even the gravity of the universe itself could be fought. The Fantastic Four had proven that when they had made their hyperspace gate.

A few months later, the greatest hearts and minds of planet Earth began working on a plan to take down a being from beyond the stars. Anyone who was smart enough was put onto the project.

Bruce had just finished high school. He was smart enough. 

He had been approached by a man named Lieutenant General Thaddeus Ross. He had been told the fate of the planet was at stake, and that his intelligence was required. 

With his knowledge of radiation, he might have an idea of how to stop something that lived in space. Apparently, Reed Richards had theories about it being evolved to deflect nuclear radiation, but Ross held out hope that they could just ‘nuke the sucker’, as he had so eloquently put it.

Bruce didn’t like Ross from the beginning, but he was hardly going to say no to such a project. When the world comes calling, you don’t hang up the phone.

“I’ll be honest with you, Banner,” Ross had said, “your GED isn’t gonna mean diddly out there in the field, so I need to know - are you up to the task?”

Bruce held firm. 

“I’m not one to back down from a fight, sir,” he said. 

Ross patted his shoulder. “Good man,” he said, a paternal smile breaching the edges of his moustache. Bruce didn’t enjoy it.

“Now build us a bomb.”

The concept had been simple enough, and Bruce knew radiation well. He was fascinated by it, how it could destabilise matter, how it was both the result and cause of atomic decay. He saw it as the life force of the universe, bursting forth in a destructive wave whenever an atom was split. It wasn’t the energy’s fault that matter couldn’t hold together in its presence - the energy wasn’t supposed to be outside the matter at all. 

The power of life was much stronger than the power of death, but that didn’t mean it couldn’t cause it.

He decided to go with gamma radiation, since it was the hardest type of energy to protect against. One needed a highly dense material, like lead or concrete, to hold back the high frequency waves.

Even a being from space would have trouble protecting against that.

He had never had a chance to test out this theory, of course, because by the time Galactus was about to arrive, Ross had shut his project down. Had said Richards and his cohorts had ‘solved the problem’. Bruce watched how close they had gotten, and was sure his bomb would have made quick work of Galactus.

Of course, a few months after that, Ross came to him again, said he wanted to restart work on the Gamma Bomb project. Said that Galactus might return, or something else just as bad, and they needed to be ready, that they’d be ‘fools not to be.’ 

Bruce told him they didn’t need to restart - he hadn’t even gotten rid of his notes.

So, Bruce, working begrudgingly with General Ross, started to put together the most destructive force in human history. 

It just wasn’t the bomb.