The army always issued blue up until the changover in 1905/07. However, contractors during the SAW made the undyed ones, and while they were mostly issued to volunteer and state units, they were known to pop up most anywhere.
The Marines used blue until around 1903, when they went to undyed ones when the army discontinued acceptance of their own blue belts in anticipation of the new clip loaders. But those would be delayed until 1907, with the Marines not receiving theirs until 1911 or so.