Change strapi iframe color style setting

Questions and Answers Strapi Design System
1

Hi, I have a web page embed Strapi using an iframe, I want to change the color style of strapi when it show in my web.

I follow the doc https://docs-v4.strapi.io/dev-docs/admin-panel-customization#theme-extension

And set something like this in /src/admin/app.js

import { lightTheme, extendTheme } from '@strapi/design-system'

const customTheme = extendTheme(lightTheme, {
  colors: {
    primary: "#f5426f",
    secondary: "#4bd92b",
    alternative600: "#f5426f",
    alternative700: "#f5426f",
  }
})
const config = {
  locales: [],
  theme: {
    light: customTheme,
    dark: lightTheme.colors
  }
};

but the color style still not change, is there any step I missed to override the color style? or it is not possible to change it?