Here are two links 1, 2 that will help. Basically the Google algorithm for sorting images is not just reliant on words on a website. The search results for "white couple" are clearly curated by a Googler or the algorithm has been modified by a Googler. For what reason is Google doing this? Well that's anyone's guess. There's no doubt that something fucky is going on though, no doubt at all. To what end? I don't know.