As of this writing, five of the top 30 titles on Amazon’s best-seller list are adult coloring books. With over 2000 titles out there and rising, the phenomenon of adult coloring-within-the-lines just ...

All products featured here are independently selected by our editors and writers. If you buy something through links on our site, Mashable may earn an affiliate commission. Coloring apps — which let ...

Add Yahoo as a preferred source to see more of our stories on Google. Think coloring is for kindergarteners? Think again! Well, it totally is, but it's also for grown-ups in need of stress relief.