How to choose different color palettes?

The palette that you see in the bottom middle of the screen is called the "Active color palette".

All recently used colors are saved and can be accessed through the "Clock" button near the "Active color palette".

 

Simply slide the names of the palettes to the left of to the right to reveal more palettes and switch between "Thematics" and "Shades".

Here you can also pick Solid or Gradient version of each color palettes in the color palette library.