Hello,
First of all thanks for choosing our Theme, we are glad to be you in the WoodMart WordPress family :-)
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Please make sure that you have used each attribute item for the product variations from the edit product.
Then you need to Go to Products >> Attributes >> Configure items >> Enable the option as in the screenshot.
Screenshot for Clarification: https://ibb.co/t4Mqxt7
Then you need to Go to Theme Settings >> Shop >> Attribute Swatches. And choose the swatch to be displayed on the product grids.
Screenshot for Clarification: https://ibb.co/fMj7mQd
OR
You can read our detailed documentation for further help:
https://xtemos.com/docs/woodmart/variable-products-swatches/
Best Regards.