On any Google Image SERP, you get a suggested list of related search keywords to narrow down your query, like this:
right click, open image in new tab to see clearly
I wonder if the colors represent a sort of heat map, the most frequently used keywords appearing in red/pink/orange, while the least used colors appearing a cold blue.
But, then I also noticed that the colors are arranged in a periodic manner. In the above case I have demarcated with a blue line the start and end of a cycle.
Apart from those two reasons, I couldn't think of anything else. My reasoning might be correct, or might be entirely wrong. Hence, my question is:
What exactly does the coloring of suggested keywords in Google Images SERP indicate?