Graphice, picture or drawing in latin, is a simple but powerful tool which lets you scan your pictures for its promeninent colors.
You can create as many palettes as you want including selecting specific regions to be scanned with in more detail to generate different palettes.
These generated palettes can be shared with to your friends and they'll be automatically saved to the internal storage allowing you to revisit them again anytime in the future.
It's also optimized for the extra display space on tablets and works great with multi-window!
Graphice is the best and most complete tool to find which colors your pictures are made of and can be extremelly useful for any graphical design project or even to craft those substratum themes.
This has direct integration with my gallery app, Focus Go https://play.google.com/store/apps/details?id=com.franco.focus.lite
With both installed you can directly generate a color palette without having to open Graphice.