Go to Product settings
(You can choose the any products)
+ Scroll down to the "Theme template" -> Choose the "product.variant_images"
+ After, click to "Alt" button in the Image
+ Fill in the name of the color in the box
+ Do it with all of the images in product.
+ After, click to "Save" button
+ Click to "View" button to see the result:
Thank for reading!