Why do most SAS troops keep wearing their new red berets even after being given permission to use their old beige ones?

In the BBC drama about the history of the British SAS elite special forces unit (SAS Rogue Heroes) the troops are instructed to swap their beige berets for red (or magenta) berets (presumably to match the berets used by other paratroop regiments).

But, in a conversation with general Montgomery (the top UK General) where the SAS leader, Paddy Mayne, wears the old beige beret and makes the argument that his highly specialised men are not like other paratroopers, Montgomery gives him permission to keep wearing the original colour.

But, later in the episode and the following episode, we see plenty of SAS men wearing the new red berets.

Why, if they have been given permission to wear the original colour, do they swap to the new one? They are, after all, known for ignoring standard military rules.

The men in his command were given a direct order to wear the regulation beret of their new regiment. Mayne famously remarked that his men should hide their berets rather than turning them in, and could wear them (around each other) when the brass weren't around.

As part of the 21st Army Group—the British formation assigned to Operation Overlord, the Allied invasion of Europe in the west—SAS soldiers were required from 1944 onward to wear the conventional red beret of airborne troops. Paddy Mayne ignored this constraint and continued to sport the beige one.

SAS: Rogue Heroes - The Authorized Wartime History

and

On October 1, 1945, the SAS paraded for the last time at Hylands House, the large estate near Chelmsford that had served as the regiment’s headquarters since March 1944. The men wore the red beret of airborne troops.

Paddy Mayne, alone, wore the original SAS beret, the color of desert sand.

SAS: Rogue Heroes - The Authorized Wartime History

and

One unwelcome upshot of the restructuring was the decision by McLeod that the SAS replace its sand-coloured beret with the red one worn by airborne troops. The decision didn't go down well with the desert veterans and some, led by Paddy Mayne (newly promoted to lieutenant colonel), continued to wear the old beret.

SAS: The Illustrated History of the SAS

and

On 1 October 1SAS paraded for the final time at Hylands House in front of Brigadier Mike Calvert. Despite their imminent demise the men were immaculate with polished boots and maroon berets. Only Paddy Mayne stood out. The man who above all others epitomised the ethos of the SAS insisted on wearing his sandcoloured beret to the very end.

SAS: The Illustrated History of the SAS

It would appear that his troops followed the order that were given, and wore their regulation gear, although the illustrated history above is replete with examples of SAS men refusing to wear tank berets, safety helmets, overseas pins and insignias, flak jackets, etc etc. These were typically issued and then conveniently 'lost'.

Lt. Col Mayne was sufficiently bloody-minded that he carried on wearing his beige beret right up to the end, and his recalcitrance was eventually seen as eccentricity rather than outright insubordination.