Fill an area selected using 'Instant Alpha' with a specific color in Photos In the Photos.app I am using Markup Toolbar in conjunction with screenshot editor.

How can I fill an area I selected using Instant Alpha with a specific color?
To fill color using instant alpha:


Select the area with instant alpha.
Press delete. If asked to save as png click yes. This makes a picture with the instant alpha areas transparent.
Selection all (entire picture) and copy.
Paint a rectangle of desired color over instant alpha areas.
Click paste. This puts back in the picture with transparent instant alpha areas over the color background.