How to change leaves to brown shades

You can also use the HSB/HSL Optional plugin to shift the shades to the desired range.

video 

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You could use Color matching. I did not mask but that should be easy task with object selector

From 2 to 1

From 1 to 2

Also Hue saturation could be a way to achieve this purpose

Another possibility.

Add a Selective Color adjustment layer.

Set something like this for Greens.

Something like this for Cyans.

Could you please post screenshots with the pertinent Panels (Toolbar, Layers, Options Bar, …) visible? 

If the leaves aren’t on Layers of their own the image would be pretty bad (edit: for this task, that is) because the masking would probably need considerable manual editing.