This plugin recurses every layer in every page of the current figma file, and detaches color styles that are backed by a single bound color variable.

detach-color-styles.ts

// This plugin recurses every layer in every page of the current figma file, and detaches
// color styles that are backed by a single bound color variable.

(function main() {
  recurseLayerHierarchy(figma.root, false);
  figma.closePlugin();
})();

function recurseLayerHierarchy(node: BaseNode, isChildOfInstanceNode: boolean) {
  if (node.type === 'INSTANCE') {
    // For instance nodes, we will only detach styles that have been
    // explicitly overriden by designers. Any non-overridden styles
    // should be detached in the main component, which will automatically
    // propogate back to this instance node. This approach ensures we don't
    // introduce unnecessary overrides in the instance.
    node.overrides.forEach(({ id, overriddenFields }) => {
      const overriddenFieldsSet = new Set(overriddenFields);
      if (overriddenFieldsSet.has('fillStyleId') || overriddenFieldsSet.has('strokeStyleId')) {
        const overriddenNode = figma.getNodeById(id);
        if (overriddenNode) {
          detachFillAndStrokeStyles(overriddenNode);
        }
      }
    });
  } else if (!isChildOfInstanceNode) {
    detachFillAndStrokeStyles(node);
  }

  if ('children' in node) {
    node.children.forEach((child: PageNode | SceneNode) => {
      recurseLayerHierarchy(child, node.type === 'INSTANCE' || isChildOfInstanceNode);
    });
  }
}

/**
 * Detaches the fill and stroke styles if they are backed by a single
 * solid paint bound variable. When this is done, the color styles in the
 * Figma UI will be replaced by the color variable instead.
 */
function detachFillAndStrokeStyles(node: BaseNode) {
  if (
    'fillStyleId' in node &&
    node.fillStyleId !== '' &&
    node.fillStyleId !== figma.mixed &&
    node.fills !== figma.mixed &&
    node.fills.length === 1 &&
    node.fills[0].type === 'SOLID' &&
    node.fills[0].boundVariables?.color !== undefined
  ) {
    node.fillStyleId = '';
  }

  if (
    'strokeStyleId' in node &&
    node.strokeStyleId !== '' &&
    node.strokes.length === 1 &&
    node.strokes[0].type === 'SOLID' &&
    node.strokes[0].boundVariables?.color !== undefined
  ) {
    node.strokeStyleId = '';
  }
}