The Klevu Search plugin already uses the labels of attributes (as specified in the Magento admin panel) as captions in the search results. To change them, please change them in your Magento admin panel.
- Login to Magento Admin Panel
- Go to Catalog → Attributes → Manage Attributes
- Choose the relevant attribute
- Click on the Manage Label/Options and specify the caption you want to use for the respective attribute
- Click on the Save config button
Once done with the changes above, please resynchronize your products.