UI components in Cosmos React use design tokens, which are a tool that helps you store the visual attributes of your application as discrete options. By using a design token, you can unify style elements across different channels, tools, and applications.
When you style a Cosmos React application on the App Studio Branding and Themes landing page, Pega Platform automatically updates the theme rule for you. However, you can gain a more granular level of control over your theme by manually editing the theme JSON file in Dev Studio.
You can search for the theme JSON file by entering the name of the theme in the Dev Studio search box, or by exploring the Rule-UI-Theme class.
For a list of design tokens and sample values, see Pega Cosmos.