WordPress block themes (also called Full Site Editing or FSE themes) use a theme.json file as the single source of truth for design configuration, including colors. This is fundamentally different from classic themes where colors were managed through PHP, CSS, and Customizer settings.
How theme.json Controls Color
The settings.color.palette section defines which colors appear in the block editor's color picker. The styles.color section sets global defaults for background and text. Individual block styles can override these defaults. Everything flows from this one JSON file.
PaletteRx's theme.json Export
PaletteRx generates a complete theme.json color configuration. The export includes: the color palette array (all your colors with names and slugs), CSS custom properties (generated automatically by WordPress from the palette), and utility classes (.has-primary-color, .has-primary-background-color) for each color.
Duotone and Gradient Presets
Block themes support duotone image filters and gradient presets in theme.json. You can define these using your PaletteRx colors: a duotone filter using your dark base and primary, or a gradient preset from your primary to your supporting color. These appear as options when editors work with image and cover blocks.
Global Styles Integration
WordPress's Global Styles panel (accessible in the Site Editor) lets non-technical users change colors within the constraints you set in theme.json. If you define 8 palette colors, editors can choose from those 8 but cannot introduce arbitrary hex values. This enforces your color system at the CMS level.
Custom Properties
WordPress generates CSS custom properties from your theme.json palette: --wp--preset--color--primary. These are available in any custom CSS you write. The naming convention is different from PaletteRx's default (--color-primary), but the values are identical.