I didn't go very far with my own benchmarks because my results were just so bad. But for example, here's a line art with the instruction to color it (I can't remember the prompt, I didn't take notes).

https://woolion.art/assets/img/ai/ai_editing.webp

It's original, ChatGPT, Flux.

Still, you can see that ChatGPT just throw everything out and does not do a minimal attempt at respecting style. Flux is quite bad, but it follows the design much more (although it gets completely confused by it) that it seems that with a whole lot of work you could get something out of it.