Alright, thread redux! I agree they're good for you. This is single-tasking with focus, creation. It can move you toward a mental state akin to meditation or quiet mind. I believe now more than ever we must create such opportunities to dwell in these spaces, and there's recreational value to engaging, it's exercise for the nonverbal mind.
We have this handy reference:

There's Krita, a free digital canvas app, with versions provided for Mac, PC, Linux. (
https://krita.org/en/)
Find a full-size copy of the OP's fox blank coloring book page here:
https://s-media-cache-ak0.pinimg.com/originals/63/5c/47/635c476c5b408a047e874a3a496688a4.pngA Krita digital canvas coloring book attempt:

Let's see more original coloring efforts shared here!
Here's another starting image selection inspired by local fauna (click for full size):
