Why Does the Hulk Change Color in the Comics?

Since the 1960s, Marvel Comics‘ resident monster, The Incredible Hulk, has just wanted to be left alone. The not-so-jolly green giant has fought tooth-and-nail for isolation and privacy, though he has often found himself entrenched in the public eye. Though he’s considered a hero while working alongside the Avengers, he’s also seen as a monster unable to be controlled. But hold on, why is he green? And, perhaps more interestingly, why does he sometimes change colors? In the new trailers for Captain America: Brave New World, we see a new Red Hulk who seems noticeably different from previous versions. What’s up with that? If you’ve also wondered this, then you’re not alone. Marvel Comics history can be a bit convoluted at times, but there are certainly answers out there.

The Hulk Is Green Because of Gamma Radiation

The short in-universe answer to why the Hulk is green is that it’s a reflection of the Gamma Rays that Dr. Robert Bruce Banner was exposed to back when he first received his monstrous alter-ego. Gamma radiation is portrayed as green in Marvel Comics (often of an emerald quality), and the Hulk is the best example of that. Other Gamma-powered characters, such as Jennifer Walters’ She-Hulk, the Leader, Doc Sampson, Amadeus Cho, the Harpy, and the Abomination all have green or greenish coloring to themselves as well, and that’s a direct result of the power running through their veins. Of course, in the real world, gamma rays don’t have any sort of coloring at all, and they certainly won’t turn anyone into the Hulk. According to Dr. Peter Petric, himself a radiation safety officer and a physicist, “you won’t turn green and you won’t get super strong” by exposing yourself to gamma radiation. Nevertheless, in the fantastical world of Marvel Comics, gamma and green often go hand-in-hand.

But there’s a more interesting behind-the-scenes reasoning for the Hulk’s skin tone. Following the tradition of other popular monsters such as Frankenstein’s Monster (at least the Universal Pictures version) and the lesser-known comic book character “The Heap,” the Hulk’s green appearance became the standard, even if it wasn’t at first. In The Incredible Hulk #1, writer Stan Lee and artist Jack Kirby introduced the world to the Hulk, only, instead of being green, he was a grey-skinned monster born of Bruce Banner’s rage. According to Lee himself, he decided on making the Hulk grey because it was “spooky” and “depressing.” But, as it would turn out, the grey coloring was difficult for Marvel’s printers to produce, so Lee was forced to shift the Hulk’s appearance from grey to green in The Incredible Hulk #2. Though technical difficulties gave us a green Hulk, readers responded well to the change, and so it stuck. It wouldn’t be until years later that the grey Hulk would return, and by then, there was another in-universe explanation: the Hulk had simply evolved.

Different Colored Hulks Are (Usually) Rooted in a Psychological Change

In Peter David’s groundbreaking run on The Incredible Hulk, the writer took the opportunity to dive deeper into Bruce Banner’s psyche. While this wasn’t the first time different versions of the Hulk would pop up, it did offer readers a real explanation for why the Hulk sometimes appeared green and other times grey. The grey Hulk personality — who is a bit smaller than the green personality — resurfaced years later, naming himself “Joe Fixit” and moving to Las Vegas to become a mob enforcer for a time. Inspired by the monster movies Bruce Banner watched in his youth, the grey “Joe Fixit” was an alternate personality who would do things that Banner himself wouldn’t. With the grey Hulk’s return, David’s run established that the multicolored Hulks were each a representation of Banner’s fractured psyche, manifesting in separate Hulk personalities with different physical appearances.

Aside from the green Hulk (often called the Savage Hulk) and the grey Joe Fixit, the Devil Hulk (sometimes called the Immortal Hulk) is a protective mechanism formed in Banner’s mind, who has a brownish/golden reptilian-like appearance. Likewise, the Hulk’s own Hulk, a personality known as Kluh, has an obsidian black-like coloring with red scars along the body. At different points, the Hulk has also taken on a red coloring (The Immortal Hulk #45), a cosmic blue appearance (Captain Universe: Incredible Hulk #1), and even an orange-ish glow in an alternate universe (Uncanny X-Force #12). Sometimes these changes are due to external factors, and other times a result of further psychological changes within Banner, but more often than not, the traditional green Hulk always makes his way back into the spotlight.

From what we’ve seen of Captain America: Brave New World, it seems as if President Thaddeus “Thunderbolt” Ross (Harrison Ford) is going to follow Bruce Banner’s (Mark Ruffalo) lead by transforming into a Hulk of his own. But unlike Banner’s green Hulk, Ross appears to be a Red Hulk, one whose power seems to rival that of his one-time enemy. While Bruce Banner’s Hulk form changes colors depending on his mental state (at least in the comics), the reasoning for Ross’ red transformation is a bit unclear. It could be the combination of both gamma and cosmic rays that gave him his power. It could be that it’s a reflection of his own “red-hot” anger and militant fury, but the comics don’t offer a specific reason for this character. As far as the MCU is concerned, we’ll just have to wait and see how Ross’ transformation is explained, including his distinct red color.

Captain America: Brave New World is in theaters February 14, 2025.