1. Go to colors/color to alpha.
2. Select the background colour of the image and ejecute.
3. Go to channels tab and right click on alpha channel.
4. Channel to selection.
5. Select a foreground colour.
6. Select Bucket Fill Tool. Select the option “Fill whole selection”
7. Fill the selection with the desired colour.https://manoftherambla.files.wordpress.com/2013/07/novias.jpg