The {color} field is often an empty field in product feeds. Most have this attribute mentioned in another field. Among other fields it could be mentioned in the {title} or {description} field.

By adding a simple search & replace rule we’re able to retrieve the color of the product from another field and print it to the {color} field and use this field in the exported product feeds.

IF {title} {contains} [Blue] THAN {replace value} OF {color} WITH [Blue]

… continue doing rules like this until you got your colors covered