How to change the lip color and enhance the shine
Open the photo you want to edit.
Select lip area with the tool «Rectangle Select Tool».
Copy and paste the selection into a new layer. Apply the filter «Sharpen» (Filters — Enhance — Sharpen) with the parameter 85 for the new layer.
Apply the filter «Dilate» (Filters — Generic — Dilate). Dilation increases the size of the bright areas in the image.
Change the layers blending mode to «Overlay» in the Layers Tab.
Proceed to the Image Layer and select lip area using «Free Select Tool». Remove it and draw over the contours of the lips with the soft-edged eraser. After that you can experiment with the layer’s opacity.
If you do not want to change the color of the lips you can discolor the inserted layer (Color — Desaturate) with the «Lightness» option.
If this effect is not enough you can merge all of the image layers (Image — Flatten Image) and repeat the steps again.