Its a fun apps that reminds me of those Doodle Art posters in the 1970s. I took off a star due to questions about in app purchases that read more like a subscription service than actual purchase. Im not sure about if I keep the pages even after the subscription ends or they are pulled. None the less, even the free pages are very relaxing to color with the Apple Pencil.
As a photographer and graphic arts, I would like to have a customized palette to track used colors. Still fun though.
Oh-Too about Adult Coloring Book - Pigment, v1.5.1