Update PRC theme reference

content/guides/react/theme-reference.mdx

@@ -6,7 +6,7 @@ description: The default theme object for Primer React components
 import {theme} from '@primer/react'
 import ThemeReferenceTree from '~/src/components/theme-reference-tree'
 
-Colors in this theme object reference CSS variables from Primer Primitives under the hood with a raw value as a fallback. We recommend referencing CSS variables directly, which you can reference from the [Primitive colors docs](../../foundations/primitives/color).
+Colors in this theme object reference CSS variables from Primer Primitives under the hood with a raw value as a fallback. We recommend [using CSS variables directly](primer/design/content/foundations/primitives/migrating.mdx) instead.
 
 <ThemeReferenceTree themeData={theme} />