I like the color pallet option you provided showing the primary colors. Adding the colors as facet options would be interesting since you can align each of the

I like the color pallet option you provided showing the primary colors. Adding the colors as facet options would be interesting since you can align each of the colors with the items, then maybe a numeric metric you can use to sort the results by the percent coverage of that color. Another item to consider is also taking into account how the user might search - "red shoes", then classify the query as "color: red" & "shoes". The next fun challenge is determining which image to display if you have a variant product (color/size combination for clothing for example). Figuring out which product image to show in the result set requires identifying the primary color in the search.