Have a look at Nilla (16 weeks old). Her father was a fawn and her mother was predominantly white. All of the other pups in the litter were fawn. She is getting darker as she ages, yet is still a wonderful light golden color.
Normally, if gold is to appear it will be within a brindle coat. If there was golden brindle in the sire's bloodline, it would explain how this Boxer came to have this remarkable light golden coat.
If you saw this color on a Beagle, it would be referred to as lemon. And with the white that appears, the dog would be a lemon & white.
While fawn itself can range from light to very dark, most often a light fawn Boxer is of a color darker than this gold that you see.
Since there is not a 'gold' option for coloring on registration forms, this Boxer would be dubbed a fawn.