The Color option was created first and linked to the Color field afterwards; Shopify leaves its swatches empty until you create it again from the field.
The symptom. The swatches show the values’ names, but no color or image.
Why. Shopify keeps swatch colors on the values of its category fields, such as Color. An option linked to that field after it was created keeps empty swatches.
The fix. On the product, delete the Color option and add it again, choosing the Color field and its values. This creates the variants again, so note their SKUs, prices and stock first. Inside the picker, option="bg-color" then paints each value’s color.