For the longest time, I always thought a notepad of blank sheets was always something that allowed more creative expression and freedom than a colouring book. (Or "coloring book" for readers from the US)
At first glance, the blank sheet of paper, a "tabula rasa" environment where you could virtually go anywhere seems a much better opportunity than a colouring book which simply offers you the ability to chose whatever colours you want so long as you stay within the lines. A colouring book seems, relatively speaking, a boring task where you have a black and white line sketch of a picture and your task is to add colour to it.
Given the choice, I usually preferred the blank sheet where I could make up whatever drawing I wanted rather than work within the framework of a sketch in a colouring book.
But situations in life aren't always like that. You often don't get to choose between the completely wide open option and the "restrictive" one.
Lately, spending time with my son, who enjoys when Mom and Dad join in on colouring with him (particularly the massive two feet by two feet colouring workbooks he has which offer lots of room for three people to be simultaneously working on the same page), I'm learning a whole new appreciation for the creative expression allowed within the "rules" of the colouring book.
Assuming you still "stay within the lines" there's still almost endless variations on the way you can fill in the colouring book.
The first obvious one is that you don't have to pick colours from reality. The grass doesn't need to be green, the sky doesn't need to be blue. You can pick whatever colours you want. You most often see this during seasonal "colouring" contests that different retailers hold where, posted near the checkout area, you see the results of 50 or more different versions of the same picture done by 50 different children. That, to me, is a wake-up call illustrating just how creative one can be while working within this "confined" workspace.
Second, you don't need to fill in every single "blank" spot -- you can choose which ones to leave the background colour of the paper. And along those lines, you don't need to actually shade in every single area in the same manner. Some can be filled in solid, some might only be outlined, some might be filled in using a pattern of sorts.
Third, you always have the option of adding to the drawing itself or breaking any area to colour in into smaller areas. There's no rule that says one area has to be all the same colour. You can fill it in however you choose, add whatever other elements you wish to the picture.
Four -- you have many options for what to use to colour the picture with. You can make it a black and white picture using a plain pencil and different styles of shading. You can use crayons, pencil crayons, markers, pens, or whatever device that transfers onto paper that you choose for your picture, or whatever combination you decide to use.
The list goes on -- and it comes from whatever comes to your mind when working on the task.
Try it yourself. Get out a colouring book and start just playing around. See what sort of ideas come to mind while you work on it. You might just surprise yourself.
Then, whenever you're faced with a task that, at first, doesn't seem to allow any sort of creative spirit or flexibility, remind yourself of this colouring exercise I'm suggesting and see what creative ways you can complete the task. IE, get to the result of filling it in while staying within the lines, but in a way that allow you to be creative and try something new.
In many ways, for me, I end up being more creative when trying to flex creative freedom within the "confines" of a space like that. Or, at least, I derive satisfaction from having completed the task which at first seems low on the creative expression spectrum, but in fact contains plenty of opportunities for me to do it my way.