I watched Dr. Strange last weekend. Now, I'm not overly familiar with the character, other than the basics. I'm sure there were changes and alterations to his character and origin story.
but, the overall basic premise of the character was still there. Rich, arrogant, selfish jerk doctor has traumatic accident which upends his world and sets him on a course to discover the mystic arts and become a better person in the process.
Strange doesn't start out as a funny stand up comic who discovers his life purpose as a doctor, then becomes selfish and arrogant, then gets into the accident, etc.
No. that doesn't happen. cuz that's not the basic story arc of the character.
Same with the visual identity. In terms of costume and appearance, he looked like Dr. Strange from the comics. He wasn't clean shaven nor did he sport a neon green Mohawk or a yellow cloak. No, he looked like Dr. Strange.
Same with Arrow and Flash. I have been finally getting around to watching their tv shows. Again, I'm not overly familiar with the characters and I am aware there are changes from the comics.
But, overall, the basic premises of the characters are intact.
Oliver Queen doesn't start out as a super sweet, hard working, productive rich kid who gets stranded on the island and then comes back a hardened vigilante bad ass. That's not Oliver Queen. That's not his story arc. Even though the show and comics differ, the basic premise of Oliver Queen is that he is a spoiled, irresponsible rich kid who gets stranded on an island which changes him into a hardened vigilante and helps him discover his "purpose."
Likewise, Oliver Queen in the show doesn't don a red and blue costume as Arrow. Or pink and yellow. No, he retains the green color scheme.
There will always be changes to these characters in these adaptations. But these characters have basic core traits, story arcs, and visual identities that define our recognition of these characters.
Deviate too much from those core tenets and they become pretty much different characters entirely.