You can add product tags to distinguish items easier and filter them easier as well.

1. Go to Products -> Product Tags
2. Create a new tag by ticking the Root to attach it to it and name it
3. You can also Rename a tag, Delete, Export or Import one 
4. Once you finished, go to Products and assign the tag to which item you want
5. Tick the item, go to the Action dropdown and choose Assign/remove tag and choose the tag you want