You'll need to be stationed at the right vantage point, looking at the correct angle to see this one

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There is a platform here that you can move with a panel puzzle

The platform also needs to be at a specific angle

Head to the purple section of the Color Swamp. There are two platforms here that are controlled by the puzzle panel between them. You will need access to the panel from the swamp, so make sure the platforms are in a position that allows this. (If you can't get to the panel from the swamp, you'll need to go the long way around to the other side at the base of the mountain.)

At this point, it might be a good idea to take a look at what you'll be doing next, before you attempt to do it. Move to the rocky area where the statue/cage are located. Take a look at the side of the moveable platform. See that circle & line? That's what you'll be tracing. As of now, however, the shape is untraceable due to the way the light bounces off its zig-zagged surface.

Now, solve the panel puzzle in the way that arranges for the platform to move towards the swamp. It will rotate while moving, allowing the shape on its side to appear to be uniform in color. You'll need to quickly run to the side where you'll be able to trace the shape as the platform turns. Hopefully you catch it on your first try, otherwise you'll have to go the long way around again to reset the platform's position.

Look for the shape on the side of this platform

Near the perimeter of the island

In one of the more colorful areas of the island

Above purple water

On the side of a yellow platform

In the Color Swamp, near the statue on top of a cage

This will require the platform to be in motion