The following conditions: is equal to / is not equal to will allow you to use individual mapping methods for individual products or product groups.
You can assign some values to products depending on what the value is equal to (or if is not equal to).
Example: You can use this option to assign the static value Red, if the value of the color field is equal to Red. If it isn't, the value Blue will be included.
You can, of course, combine this one with many other conditions, for example, to create a rule for every color in your shop.
Although the two simple rules should cover all the products, it is recommended to always have an extra rule for other products (not covered by the rules)—to make sure there are no empty values in your output feed.