What do you mean dark brown with tan spots? Did his ear have spots or did his fur have spots?
Many tans have freckles on their ears so he could be a tan. Did he have a white belly? If so, then he'd be a beige. If the color was the same all around the belly then it'd be a tan.
If it had a dark brown mask and veiling then it'd be a brown velvet.
Or if it was white and brown spotted it'd be a tan white or pink white
So it really depends on what it looked like, there's many types of "brown" chins.