Interesting, what AI are you using to generate these? Are these straight from the net or is there a post processing pipeline? If so, what are you doing?
Not the GP, but inspired by your question I tried asking ChatGPT to create similar coloring sheets. The results seem suitable for coloring. Here's one prompt: "A simplified line-drawing coloring sheet of a dog flying an airplane. The drawing is in clean black lines on a white background, with minimal details and clear, bold outlines."
Later: The prompt worked with Imagen 3 on Gemini Advanced, too:
