Swatches are assigned per attribute. Currently, you can choose from any of the following swatch types:

• Image Swatch
  Upload an image to your media library to use it as a swatch. It will use the ‘thumbnail’ size from your media settings.
• Colour Swatch
  Select a colour to use as a swatch.
• Text Swatch
  Use the attribute label as a ‘tag’ style swatch.
• Radio Buttons
  Use the attribute label as a ‘radio’ style list.