Variation Products can be listed out to your channels together, but they can also be listed individually to your sales channels.
To list a single Variation of a Product, go to the Products tab and select All Products. Find the Parent of the Product you want to list and click on the title to reach the Edit Product page.
From the Edit Product page, go to the Variations tab to view the variations for this specific product.
Find and click on the SKU of the Variation you wish to list. You will be directed to the Edit Product page of that particular Variation. From here, click the Create Listing button on the top right hand side of the page and select the sales channel of your choosing to start the listing process.