The color on your slides is assigned through a Color palette of your choice. There are several preset palettes to select, and you can create your custom one.
To get there, on the Design tab look for the Palette button.
Our pre-designed color palettes will display. Select the one you want to use and it will automatically be applied to all your slides.
The Plus button allows you to add a new color set to the palette.
You can assign up to three different color sets. Each set can have three different colors, assigned to a specific content block of the presentation: texts, backgrounds, and highlights.
To change a color just click on it, or type in its HEX code.
Once you have your palette and it's color sets, you can change colors on a specific slide. On the Design editor, click on the background of your slide and the different options will be seen on the right side of your slide.