GX Theme Styles is a Firefox add-on that enhances personalization by allowing users to customize their browser themes. This extension offers a variety of preset themes inspired by the GX style, which are compatible with both light and dark color schemes. Users can modify multiple elements of the browser's appearance, including the background colors of tabs, toolbar, and accent colors. Furthermore, it provides options to change font colors for unselected tabs, selected tabs, and panels, ensuring a cohesive and personalized browsing experience.

One of the key features of GX Theme Styles is the ability to customize button colors for hover and active states, enhancing interactivity. However, it is important to note that the add-on has certain limitations; it works only with solid themes and may cause issues when applied to themes with images. Users must also adjust specific settings in the Firefox configuration for optimal performance with dark themes. Overall, it is a comprehensive tool for users looking to tailor their Firefox interface.