This was a just a simple request I got. Trained on a collection of images from DarkZeroAI. Note that this style tends to gravitate towards simple backgrounds. For more detailed backgrounds, you should specify detailed background in your prompt or simple background in your negative prompt.

I recommend using this LoRA with WAI-ANIMA: https://civarchive.com/models/2544636/wai-anima
A strength around 0.85 is good.
Use trigger words: darkzeroai-style, flat color, anime coloring, anime screencap