Would it be possible to generate URLs for all the product variables and therefore give Google the opportunity to index the single variable in addition to the main product?
Woodmart has the feature to display single variations with unique URLs. This helps Google index each variation separately. Just ensure variations are enabled in the theme settings, and each variation will have its own URL, like ?color=red&size=large. You can further optimize with an SEO plugin like Yoast to make sure each variation is indexed properly by Google.