Red enhance method 1

Fill second copy with FG colour

In the layers dialogue select Background copy#1.

background copy#1 selected

Double click on the Foreground colour in the main GIMP toolbar and type in the hexadecimal code 808080 (grey) in the HTML Notation option box.

foreground colour button grey foreground colour

On the image toolbar choose

Edit » Fill with FG Colour

fill layer with grey

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