In order to configure Open Graph Tags for Magento 2 Blog Category Page please go to Content > Blog > Categories and click on the category you're most interested in to start configuring.

Open graph tags blog categories

On the blog category page find the Open Graph Metadata section.

Blog category page open graph metadata

 Open Graph  Metadata

1. Set the OG title. In case you haven't set it up the Meta Title will be used. If it isn't configured either Blog Category Title will be used.

2. In the OG Description set the Open Graph description of the category. Category Meta Description will be used in case an OG description hasn't been set up.  The Default Description will be used, if there are none of the descriptions configured.

3. In the OG Image set the Category  Open Graph image (Facebook Image). If you haven't set it up the Default OG Image will be used.

Blog category page open graph metadata

Once you've finished the configurations don't forget to press the Save Config button.

Blog category page open graph metadata save