Color Power! - 10g
Got the Red Star Ring by using an Orange Wisp in PLANET WISP Act 2 and reached the goal.
This is close to the end of the level. Go through the level like you normally would; direction does not matter. Eventually you will come to a large area with mine carts going every which way. Keep going until you land on a piece of machinery with mine carts coming out of the background and heading to the left. You want to jump on one of these carts. You’ll know this is the right area because a little ways down the track is three red hoops that you can jump through with fire on either side. Jump through these hoops.
You’ll then be on another piece of machinery with mine carts shooting out of it towards the left. Hop on one and follow it down the track. Go slow to prevent any mistakes. If you fall, try to find a rocket wisp so you can get back up. A little bit down the track you’ll see a rocket wisp above you. If you don’t already have a rocket wisp, grab this one and continue down the track. Near the end of the track is three more red hoops, but just before that is a bunch of rings indicating where you should use the rocket wisp. Use it there. You should grab the red ring on your way up.
Just finish the level and the achievement will pop.
Update - I've changed the video below because I think it better shows the ring. Skip to about 3:25 to see where to start to get the red ring. Full credit to Aura313Productions of Youtube for the video.