Coloring Books for Relaxation

As a girl, (and a mom and grandma) I have always enjoyed coloring.
Now, it seems to be the popular thing to do.

But the coloring books are much more complex.

And it's better to use colored pencils rather than crayons.
My daughters and I received coloring books for Christmas this year, 
and we're enjoying them immensely. How about you? Do you color?