Interactive Fill

We start with a pre-defined mask (see Masking video).

Next, we will fill the masked area to change the sky color.

Click the Interactive Fill tool. Drag to define a gradient from black to white (default colors).

Drag colors from the color palette into the top and bottom handles, or add additional colors to the fill.

Press Enter to apply the interactive fill to the image.

Press Ctrl+R to remove the mask.