Using images or colors as a selection button for a product variation gives a much better way to present the information. Why ? Because the cognitive weight of this click is much less than if it were a word. We understand immediately seeing the same t-shirt proposed in red, yellow, green and blue that these are its variations; no need to interpret the information.
If you need a demo to convince you, go to the site where to download this plugin, you will be able to access the test link of the demo online.