Bright Outfits for the Queen
It isn’t a fashion choice of the Queen to wear the bright outfit when in public, but it is an intelligent decision. The rules she needs to follow are to wear bright clothing when she is in public for the people around her to spot her without any difficulty easily. It was not clear why it was necessary for the Queen to wear the bright outfits until her daughter-in-law Sophie, the countess of Wessex, revealed the reason in the documentary.
The Queen attends many public appearances, and being surrounded by more than a dozen people is nothing new for the Queen. Still, it is very realistic and logical for her to wear bright clothing to be very noticeable not only to avoid unforeseen situations but also to be prominent.