I've spent dozens of hours learning and testing prompts for coloring books. I even published one on Amazon.

Here are all the tricks I learned.

PS: Replace what is inside <> with your design idea

Mandalas

mandala background, coloring book page, clean line art

Patterns

<flower> pattern background, coloring book page, clean line art

Realistic Drawing

<a dog>, clean line art, coloring book page, white background, 2d

Realistic Drawing with Mandala style

<owl>, coloring book page, clean line art, mandala background

Children Style

cartoon of a <dog>, children coloring book page, white background

Final Adjustments

Midjourney images still need additional upscale for printing if you want the best quality. I used BigJPG; it's free for a small demand.

Parameters:

• --no color (this helped me get more consistency)

• --ar 3:4 or --ar 2:3 best aspect ratios for printing on normal pages