A.M.
I've had success with Feria #100, I think it is called light blond. It has a gold undertone in my hair, a little warmer blond then white blond. I've paid to have lt golden highlight/coloring in my hair before and this is not that much different for the end result. I have naturally blond hair too and it gets a little dishwatery looking by late fall.
Update - - One more point, the first day or two after coloring it appears slightly more gold then the true end result. After a few washes, the excess colorant comes out and leaves the natural blond look. I just colored my hair again with this and thought I'd mention this so no one freaks out if it is slightly more golden at first or a little more than you expected once done coloring, give it a few washes and a few days to adjust. And - the conditioner that comes with the Feria rocks!