That’s awesome that you’re already using our app!
To delete variants in a collection you would need to do a search for products in the collection, and then add another condition for “Option 1 Name” that equals “blue”, or what ever value you’re looking for. Then after you click ‘Edit Products’, choose the ‘delete variants’ option.
Please note that deleting variants is permanent. If you’d like us to look over the edit before you run it you can reach out to support@ablestar.com and we’ll make sure everything looks good before you do the deleting.