The "Coloring Fun" book will teach you - among other things - how to build coloring spreadsheets, with all their formulas, control cells, and Conditional Formatting rules. If, however, your main interest lays not in creating such pages, but just in coloring per se, you may buy the companion coloring albums to this book.
These albums are actually the Excel files pre-filled with formulas, Conditional Formatting, etc. Each file is a collection of several sheets. Each sheet has a picture area and a few control cells:
The cells with strange names ("Divisor", "R_power") are here to create new patterns. Changing values in any of them will change - most often, quite unpredictably - the picture. For example, the Divisor is 0.16 in the picture on the left. Changing it to 2, and leaving all other parameters the same, will radically transform the pattern (see below, left).
Now, keeping the new Divisor value of 2, let's replace R_power with a different value as well, and the pattern will change again (below, right):
Since we have several parameters to change, and each of them may be almost anything, there are endless pattern possibilities. Here are a few of them, obtained with different formulas:
And then, after choosing a pattern, you'll begin a second quest: picking a suitable coloring scheme. A few clicks will easily change the picture's ambience:
I showed one of these files to my 8-year old niece - and couldn't tear her away from it! So if you want to make an artistic (and at the same time educational) gift to a child- or to an adult, for that matter - pick a couple of coloring albums at LeanPub, along with detailed instructions of how to use them: