When you add a tag (ie: rainbow), it will be indexed in the tags attribute.
When you add a key:value tags (ie: color: rainbow), it will be indexed in the named_tags attribute, and the named_tags_names attribute will hold the property names (in this case, color).
If you'd like the named_tags and/or named_tags_names values to be searchable, you can add these attributes as searchableAttributes in your Algolia index configuration.