With Color by Number, for example, you can get a free three-day trial, then the app costs $7.99 per week. There are monthly and yearly subscription options too, which cost $19.99 and $99.99 ...

One page in the book, for example, instructs you to color by the numbers on a Sudoku grid. For another drawing called “Coin Hex” in a section on randomness, you choose two colors, assign each to a ...