Using background eraser then creating new background color

[Grenou]

This is the picture I am trying to edit.

I want to erase the background, which the background eraser tool does wonderfully, but then I want to add a new background color.

Once you have removed the background, click on Layers>New Raster Layer.

This will add a new layer in the Layers Palette. Drag it under the layer of the image you have just worked on, or click on Layers>Arrange>send to bottom.
Fill this layer with the colour of your choice.
Merge All.

:-)
Grenou