When using the gatsby-plugin-theme-ui plugin with Gatsby, it is not using the initialColorMode in the /src/gatsby-plugin-theme-ui/index.js file, and instead, it is using the dark mode directly.

Take this theme as an example:

export default {
  initialColorMode: 'light',
  colors: {
    text: '#000',
    background: '#fff',
    primary: '#6e67ff',
    secondary: '#212121',
    modes: {
      dark: {
        text: '#fff',
        background: '#212121',
        secondary: '#fff',
      },
    },
  },
};

It should use the light mode as the default mode, but instead, it is using the dark mode with no reason.

Here is a reproduction of the issue: https://codesandbox.io/embed/gatsby-starter-default-qyqkp