play with your iso more, the pictures look a little bright, give it a try
also shoot raw files so that you can get photoshop if you dont already have it, and tweak the colors a little bit
last tip, youre off to a decent start, i know because i ride sunday river that the angle you shot that rainbow at youre looking into the sun, and you want to try to have the light behind you almost always, but there are exceptions, but once again shoot raw, because those are the best pictures because you can toy with them