Altering background colour of an image

@ViewAhead -I use a photo editor on my laptop [had the same one for years] and I was moaning recently that they've added more 'stuff' which I probably wouldn't use, one of them being a tool to change the background colour.
I thought I'd try it after reading this thread, but - it's 'slower than a week in the jail' as we say here.
I'll leave it for now to do it's thing -maybe go on a week's holiday.... and I'll let you know if it's any use!

That looks great though - the job @Palustris has done

 

It took me about 30 minutes to do that image for View Ahead, once I had worked out how to do it.

 

A very productive 30 mins!

 

I had to go out, so I didn't have time to wait half an hour for the one I tried @ViewAhead !
I might try again - maybe this morning instead of doing what I should be doing - housework and baking...