You could use some stencils or stamps to make a pattern or irregular pattern with a color you do like, if you can tolerate the old blue coming through. For the inside, if you don't want to take the lining out/bag apart, you can either hand stitch a new lining to the old one, hot glue it in, or sew some snaps all around the inside top and snap a new lining in.
Or you can do the opposite and put the snaps on the outside and make a new cover. Though that might be just like making an entirely new purse.
Does leather bleach? You could try some bleach stencils, maybe.