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CSS variables, also known as custom properties, allow you to define reusable values that can be dynamically changed to update theme colors across your website. :root { --primary-color: #3498db; --secondary-color: #2ecc71; } body { background-color: var(--primary-color); color: var(--secondary-color); } .theme-dark { --primary-color: #2c3e50; --secondary-color: #ecf0f1; } Toggle Theme function toggleTheme() { document.body.classList.toggle('theme-dark'); } ADDITIONAL COMMENT: CSS variables are defined using the syntax "--variable-name: value;" within a selector, often ":root" for global scope. To use a CSS variable, apply "var(--variable-name)" in your styles. JavaScript can manipulate CSS variables by toggling classes or directly updating styles, enabling dynamic theme changes. Ensure that the CSS variables are defined in a scope that matches their intended use, such as globally or within specific classes. ✅

How can I use CSS variables to change theme colors dynamically?

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How can I use CSS variables to change theme colors dynamically?

Asked on Oct 02, 2025

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CSS variables, also known as custom properties, allow you to define reusable values that can be dynamically changed to update theme colors across your website.

<!-- BEGIN COPY / PASTE -->
    <style>
      :root {
        --primary-color: #3498db;
        --secondary-color: #2ecc71;
      }

      body {
        background-color: var(--primary-color);
        color: var(--secondary-color);
      }

      .theme-dark {
        --primary-color: #2c3e50;
        --secondary-color: #ecf0f1;
      }
    </style>

    <body>
      <div class="theme-toggle">
        <button onclick="toggleTheme()">Toggle Theme</button>
      </div>
      <script>
        function toggleTheme() {
          document.body.classList.toggle('theme-dark');
        }
      </script>
    </body>
    <!-- END COPY / PASTE -->

Additional Comment:

CSS variables are defined using the syntax "--variable-name: value;" within a selector, often ":root" for global scope.
To use a CSS variable, apply "var(--variable-name)" in your styles.
JavaScript can manipulate CSS variables by toggling classes or directly updating styles, enabling dynamic theme changes.
Ensure that the CSS variables are defined in a scope that matches their intended use, such as globally or within specific classes.

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How can I use CSS variables to change theme colors dynamically?

Asked on Oct 02, 2025

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