Hello,
Thank you for contacting Rank Math and bringing your concern to our attention. I’m sorry for any inconvenience this issue may have caused you.
I’ve checked the attribute, and it seems that it is set to index.
To set them to noindex and remove from the SERPs, head over to Rank Math > Titles & Meta > Product: [Attribute] and set the Robots Meta to No Index

Once done, give Google some time to recrawl your site and deindex the attribute URLs.
Hope that helps.
Thank you.
Hi Reinelle,
Yes, it worked!
Thank you very much for your fast response!
Kind regards,
Julius
Hello,
We are super happy that this resolved your issue. If you have any other questions in the future, know that we are here to help you.
If you don’t mind me asking, could you please leave us a review (if you haven’t already) on https://wordpress.org/support/plugin/seo-by-rank-math/reviews/#new-post about your overall experience with Rank Math? We appreciate your time and patience.
If you do have another question in the future, please feel free to create a new forum topic, and it will be our pleasure to assist you again.
Thank you.