To show product images for a specific variant take the following steps:
1. Go to Online Store > Themes > Customize > Products > Product information.
2. Enable the Hide other variants’ media after selecting a variant option.
3. To group multiple images to a variant you will have to add the first option value to the image alt text separated by a |. Ex Description | Crimson red
To add the alt text to your images as described in step 3 take the following steps:
1. Go to Products > your desired product.
2. Upload your images.
3. Click on your image.
4. Click Edit alt text.
5. Add your alt text as described in step 3. If your variant name is Crimson red your alt text should be Description | Crimson red. The first half is your standard alt text description, the second half is the name of the variant that this image should be associated with.