Once a distinctive unit insignia is approved, it is changed only when a heraldic or historical error is found. A modification of unit designation or mission does not permit a change to the DUI design. As a result, DUIs tend to further reflect the historic roots of a unit. For example, many older Military Intelligence battalions' DUIs feature teal blue rather than oriental blue, having been designed for Army Security Agency units which were designated as branch-immaterial. Likewise, those that began as Signals units typically feature orange. The 211th Military Police Battalion provides an example of a unit changing branches without changing insignia, having been assigned to six different branches during its existence. Color-bearing battalions and regiments continue to have insignia without the shield shape if they were formerly non-color-bearing units when the insignia was approved; this includes not only former groups and brigades that were downsized, but as well flexible battalions (i.e., battalions composed of variable attached numbered companies, rather than fixed-TOE battalions composed of lettered companies which are organic to the battalion) which gained coats of arms and thus colors in the late 1990s, long after their DUIs were already approved.