Puzzle/Puzzled

Had this little puzzle ages, the idea is to change the position of the pegs by moving one peg at a time so the colours are reversed. Think I did solve it once, but can't remember how!
Anyway, it makes another indoor blip for a cold, grey and icy day.

One of the blue pegs seems to have been chewed by something. Again, can't remember when that was. Could have been my dog, but she would have swallowed it! Blame it on a mouse.