The only downside is the need to have a very wide range of colors. Indeed, on some drawings, we are forced to juggle between 3-4 shades of brown, green, blue ...
It is not always easy to find the right color to bring out the design. I had a few missed at this level for some coloring. Fortunately there is always the "solutions" to the end of the book to see the real picture and the gradient necessary.
Maybe it would have been interesting to make a standalone unit with suitable color pencils numbered to properly do the coloring.
