I took this pic under one of the big trees at work - the soil is pretty sandy and nothing much grows there. It wasn't very orange so I had to process the colour in (not quite in keeping with the rainbow challenge, but I didn't have time to track down orange sand!). I like it better this colour anyway! (It was greyish-brown before).
I think you did a great job with this! And there's nothing in the rainbow challenge rules that says you can't manufacture the color! I like those two leaves in there for good measure as well!