Bunnies don't completely change their color like hares do, but they can look a bit different for each moult. Might be that they've gotten sunbleached over the summer, and when they moult the bleached fur falls of, leaving behind their "natural" colors once again.
Also many markings change as the rabbit gets older.
Zakura is a nice example of this:
Baby Zakura
Zakura today. Quite much darker in color.
Sasuke can look very different in summer and winter, depending on how much time he spends in the sun.
Sasuke in the winter
Sasuke in autumn. Mid-moult. The golden-brown fur is how he looked like last summer.
Aroma's changed a lot during her life.
Baby Aroma, taken by her breeder.
When I first got her, at three months of age.
Adult.
And now...moulting season has began. :roll: