I’d say this is more a hands-on workshop in book form than I would say coloring book.
But don’t get me wrong, it is definitely a coloring book.
You are basically walked step by step through color theory, and how to implement it to create your own color pallets.

The colored pencil I added myself, thats how its hands on, you fill in the color as you read.

I selected a basic color scheme based on the color wheels I colored in, and then I applied that scheme to two mandalas, taking different approaches in how I applied the colors.

I used the same set of pencils in both mandalas, unfortunately, my original red-violet pencil lead was shattered, and I had to switch to a different brand, so the hue was a bit different.

The book says right there in the title PENCILS. The paper is a little thin for markers, you will have bleed through. The first quarter of the book is lesson material, and it is printed on both sides of the page, you will definitely not want to use markers.
The Inspiration and mandala pages are printed with a colorable image on one side and information about that image on the opposite, so again not really a good fit for markers.
This book is available from Amazon: https://www.amazon.com/Color-Theory-Pencils-Mandalas-Devine/dp/069295287X
Dawn is a professional costume designer and costume historian. Her approach to creating this book was one of academic sharing, it really is a learning tool for color theory. You don’t need expensive colored pencils, and you don’t need a big set either. I made sure to complete this with a basic set from Crayola. You will need a pencil set with at least 12 colors– not black, white, beige, or brown, but the hues you would find in the rainbow and then some.
