How do I remake this image? I want to make the gray, green and blue part.
It basically is a slightly altered rounded rectangle. I was wondering how to make it fit the curve of the circle perfectly.
With Photoshop CS6, CC or CC2014 you can easily accomplish this with just a circle shape and the stroke features.
(Note the animated GIF linked is 800k so I purposefully did not put it inline for this answer.)
"I want to make the gray, green and blue part. It basically is a slightly altered rounded rectangle."
That is not the best way to see it. You should look at it instead like you have a circle - maybe all in one color at first, that had a stroke but no fill. Then you use the "Add Anchor Point" tool to mark segments you want to cut out of it, and delete them.
Be sure your stroke end caps in the shape tool toolbar are set to be rounded off instead of square, you'll get the effect like this:
That'll gets you the shape. But to have Photoshop color the strokes differently, you'll need three different layers for each color: gray, blue, and green. So once you've cut it up, move the stroke pieces to their own layers.
Honestly this is not such a great Photoshop task, because it's harder to make the cut points in a symmetrical way.
Photoshop makes it a rather difficult but Its still doable. here's how I do it:
Make the circle as you would and mark down its centre using guides
Cut into the circle with another circle through the centre. Now here if you have a rough Idea, how thick a circular line you want, you can create the first shape lets say 500x500 px and the cut into it with a circle of 480x480 px for a 10px thick circle. Its really important that you have guides and all other informative options on to make this easier. merge the shapes
Now(You will really need guides to do this right) depending how much of a circumference you want make a shape over the circle using pen tool like so. You can use masks here as well but the raster will hurt your options incase of resizing.
Duplicate it and combine the rough cutting shapes. then merge them
Now while you have the cutting shape selected with the path selection tool merge the circle and the shape.
Now using the shape modes select Subtract from front shape then select merge shapes to get the basic cut of the circle
Now here knowing the circumference width will save you a lot of trial and error. My width is 25 px so I create a 25x25 px circle and then Align it to the cut circle to get the desired result after a little duplication and merging
There might be better methods out there but for Photoshop this assures the best symmetry for me. Hope it helps!