##Global Default Color Scheme
Head over to the admin section of Looker (/admin) to set a default color scheme for your instance. On the first page, you’ll see a section called Default Visualization Colors
Choose a color palette here using the color picker or by entering hex values into the input box.
The colors defined here will apply to all new charts made on your instance, and any old chart whose colors had not ever been adjusted from the Looker defaults. Users will be able to override these colors as they create individual charts, and access them as a “Default” color palette in the editor on the Explore page.
To learn more about using color palettes and the color picker, check out this article