The MCU draws heavily from the comics, but not everything is the same. Some of the major events that happened both in the comics and in the cinematic universe happened differently. For example, the Avengers formed under different circumstances, and Captain America wasn't even one of its founding members - instead Wasp and Ant-Man were. And there's also the case of the Civil War which led to Captain America's death in the comics - but not so in the MCU.
Another change concerns the way the characters look. More often than not, their portrayal in the MCU differs from the comics, and that includes side characters as well as main heroes.
Hawkeye
Hawkeye has multiple looks in the comics but one thing that almost consistently remains different from his portrayal in the MCU is the color palette. Hawkeye in the comics usually wears more colorful clothing than in the MCU where the color black seems to be his preferred choice. He also has blond hair and blue eyes and is 6ft 3inch tall. Jeremy Renner, on the other hand, has brown hair and is much shorter than the comic-book Hawkeye - he stands at only 5ft 8inch.
Thor
Unlike his fellow Avenger Hawkeye, both comic-book and film Thor have long blonde hair and blue eyes. There's a difference in height between them, though - Thor is 6ft 6inch tall, making him 3 inches taller than Chris Hemsworth. Costume-wise, Thor lacks his iconic helmet in the films. He also later lost his iconic long locks, courtesy of meeting Stan Lee's hairdresser in Thor: Ragnarok (2017).
Iron Man
In recent years, Tony Stark has started to look more and more like Robert Downey Jr. in the comics as well. But that wasn't always the case. Previously, Tony Stark had black, or sometimes dark brown hair. And he possessed piercing blue eyes. He also stands at 6ft 1inch (without the armor on), while Downey Jr. is only about 5ft 7inch tall.
Captain America
Unlike his good friend and occasional enemy Iron Man, Captain America in the MCU looks quite similar to his comic-book version. Both of them have blonde hair and blue eyes.
Even though Chris Evans' hair in the MCU wasn't always clear blonde, sometimes it was closer to light brown. Either way, they're similar enough to be recognizable, despite the 2-inch difference in heights for comic-book Steve Rogers.
Doctor Strange
Of all the MCU superheroes, Doctor Strange is one of the ones fairly close to his comic-book portrayal. Depending on the source material, sometimes his hairstyle differs from the films. What remains is the dark color of his hair (with hints of grey) and cold blue-grey eyes. The biggest major difference then is that the comic-book Stephen Strange is at 6ft 2inch 3 inches taller than Benedict Cumberbatch.
Captain Marvel
Marvel has its fair share of blonde, blue-eyed superheroes. That's also the case for Carol Danvers aka Captain Marvel. Similar to the case of Doctor Strange, comic-book Captain Marvel looks a lot like the film version portrayed by Brie Larson - and the main difference is once again the height. In the comics, Carol is 5ft 11inch, but Brie Larson has a more common height for an American woman - 5ft 6inch.
Scarlet Witch
Just like her fellow Avengers, Scarlet Witch has had multiple looks in the comics. However, her most iconic appearance is the one with the headband. For now, she doesn't have it in the MCU but could sport this look in her upcoming TV series WandaVision.
Otherwise, the MCU Wanda Maximoff looks fairly similar to her comic-book counterpart. Wanda has green eyes, auburn hair, and is 5ft 7inch. Elizabeth Olsen also has green eyes and she sports auburn hair (reddish-brown) in the MCU. The one significant difference is that Elizabeth Olsen is 5ft 4inch, not 5ft 7inch.
Black Widow
Black Widow's most recognizable feature is her red hair. And besides the brief stint with blonde hair in the MCU, Natasha Romanoff mostly stuck with the red color. Those who don't read the comics might not know that just like the MCU Black Widow, Natasha also changed her hair color for a time in the comics. Except she didn't dye it blonde but went black instead. Natasha has blue eyes and is 5ft 7inch tall. Scarlett Johansson's eyes are green, though, and with the height of 5ft 3inch, she's one of the shortest major actors in the MCU.
Spider-Man
Even Stan Lee himself approved of Tom Holland's portrayal of Spider-Man and said Holland looked like Spider-Man, or really, Peter Parker, should look. Peter Parker isn't the tallest of superheroes in the comics - he's 5ft 10inch. However, Tom Holland stands shorter at just 5ft 6inch/5ft 7inch (there are still disputes about his exact height). What is, nevertheless, correct, is his hair color and eye color. Just like Holland's, comic-book Peter Parker has brown hair and brown eyes.
Bruce Banner
Finally, let's look at everyone's favorite angry green giant - when he's less angry and not a giant. Physically-wise, Bruce Banner doesn't draw too much attention to himself when he's not Hulk. Just like Spider-Man, he's of average height, 5ft 10inch tall. He has brown hair and brown eyes hidden behind his glasses, and he's not very muscular. Mark Ruffalo is older than his comic book counterpart which accounts for his greying black hair. Just like many MCU actors, Ruffalo is also shorter than the superhero he plays - he's 5ft 7inch tall. What remains the same is the color of his eyes, dark brown - also often slightly hidden by his glasses.