@tobejacob/myextension/src/browser/style/index.css

The example extension demonstrates how to contribute a custom widget (i.e. a view or editor) to Eclipse Theia. Furthermore, the template contains an example unit test.

#widget-container h2 {
    color: var(--theia-ui-font-color1);
    font-size: 12px;
    font-weight: 400;
    padding: 10px;
    text-transform: uppercase;
}