theme.getCurrent()

windowId Optional

integer. The ID of a window. If this is provided, the theme resolved is the one applied to that window. If it is omitted, the theme resolved is the one applied to the most recently focused window.

A Promise. The promise is fulfilled with a theme.Theme object representing the theme applied to the given window. If no extension-supplied theme has been applied to the given window, it is fulfilled with an empty object.

Gets the properties frame and toolbar colors of the current theme:

function getStyle(themeInfo) {
  if (themeInfo.colors) {
    console.log(`accent color: ${themeInfo.colors.frame}`);
    console.log(`toolbar: ${themeInfo.colors.toolbar}`);
  }
}

async function getCurrentThemeInfo() {
  const themeInfo = await browser.theme.getCurrent();
  getStyle(themeInfo);
}

getCurrentThemeInfo();

• theme-integrated-sidebar