Hello,
When the “Show single variation” option is enabled, each variation of your variable product is treated as a separate product on the archive pages.
This setup inherently conflicts with the display of grid swatches, which are designed to work with grouped variations.
Unfortunately, it’s not possible to show color variation swatches on the product grid with this option enabled. To achieve your desired outcome, you would need to disable “Show single variation.”
I hope this clarifies the situation. Let us know if you need further assistance!
Best Regards.