Color is automatically applied throughout the deck, just by selecting a Palette. Here is how to make color changes in your slides.

Go to Palette, in the Design editor to see the list of preset palettes to choose from. Each one has different sets of color combinations. Color Sets are designed to ensure a good result, making things easier for you.

You can change the color combination on a slide, by choosing a different Color Set. For that, go to Background in the upper settings menu bar to find the Color Sets and try them out. This will change color only for the selected slide. 

To change text color, try a different Color Set. Keep in mind that color can't be changed for individual elements or text. Some palettes may not have different text color options in their sets.

To choose a specific text color for a slide, you can create a custom Palette. This is a Premium feature.

To create your own Palette, hit the "+ New Palette" button, up in the list of Palettes.

Your palette can have up to three different Sets and each set can have three different colors. You are able to choose colors for texts, backgrounds, and graphic highlights. To set up a color, just click on it to access the color wheel or type in its HEX code.

Save the Palette to access it from the Palette options in the editor, even for other presentations. You can also hit the pencil button to edit the palette.