If you're looking to do this one yourself, I can offer a few suggestions that will help clean her up. The legacy leather is very forgiving when it comes to cleaning and I have found that if I clean my leather bags like I do my saddles, boots, and other leatherware that I use for riding, that they are easy to keep in good condition.
To clean the leather, I recommend finding a tin of Kiwi Saddle Soap. It's about the size of a hockey puck and is the color green that your bag is, coincidentally. It's much richer and creamier than regular glycerin saddle soap and it has worked wonders when treating dried out leather. Use a clean sponge and warm water. Wet the sponge and work some soap into it from the tin. Then apply it to the bag in a circular motion.
If you're looking to blend in the water stains, work the soap into the middle of the stain less than into the regular areas of the bag, and then just barely clean the edges of the stain. This will help fade the color across the border of the stain so that it's less noticable. This soap will not remove the dye from the leather, but will instead brighten the color and make it richer, especially after it has been conditioned.
As you're working, make sure to change the water when it gets dirty, and rinse your sponge often. After working soap in to a panel on the bag, rinse your sponge and wring it out, then wipe off any lather. You can use a soft towel to wipe the surface of any excess water, but don't "scrub" it dry. Once you've gone over the entire bag, I would suggest turning it upside down over something so that all surfaces of the leather can dry evenly.
Don't be alarmed if the leather looks darker while it's wet, it will lighten as it dries. Once it's pretty dry (I usually wait 45 minutes to an hour), condition it as you normally would. Apple conditioner is fine, or I can also recommend Lexol conditioner (not oil - this will darken the leather).
If you try to mind the edges of the water stain when you clean it again in the future, they will eventually blend in completely, but unfortunately, there is no way to remove a water stain in one go.
This is the type of treatment a cobbler would give your bag and will, in the end, refresh the color, brighten and clean the leather, and leave the bag looking much richer and healthier.
I hope this helps!