Perhaps, but early on in the organization of the GAF the Scout Commander came up with a green flag and so it became. Given that official WHITE scout units, outside of Forsyth, didn't actually exist, the color of the guidon is actually kind of moot.
The Corps of Marines flag is red, but it really should be blue based on the Corps' colors in the 19th century.
In the interest of morale, I see no reason to change the guidon color unless the Scouts decide to.
US Scout
GAF Chief of Staff