Chroma Key Problem in Final Cut Pro X

It’s keying blue. Click sample color and drag across a portion of the green screen.

It looks like both the green and the blue have been keyed out.

As a test, make a new project, add the greenscreen clip and the background and add the Keyer effect, without any more changes. What do you see?

open the clip. Copy the contents, paste into a new project.

A few things: first, just press command-shift-4 and drag a rectangle to take a screenshot. No need to use a camera or phone to take a screenshot.

Second, you've shown us the composite; please show us what the original and the matte look, so we can have an idea of what the person's clothing compares with the background.

Sample color is a tool. Select it and drag a section of the green screen for it to sample. Did you do that?

How long was the project? See if any of the clips are that long. Sometimes users opens clip and edit into it rather than into a project.

I did a test with the image that you posted. In my mac it keyed the green.

I can understand how it might, as Tom said, key the blue, but that does not square with the "Original" already showing the shirt keyed out.

Try a separate test as I suggested before, and tell us - does it key the blue? Do as Tom said. Does it key the green? Maybe there was a weird glitch.

Yes. If you add a second Keyer it will go for a different color, usually blue. Normally you use a single Keyer and adjust the controls to key a single color.