Green card in football: What is it for?

Yellow and red cards have been used in football for decades now, but is it time for a green card to be introduced on a permanent basis?
In January 2023 a referee made history by showing a white card for the first time ever during a clash between Sporting Lisbon and Benfica.
The first use of the green card by a referee happened in June 2018 during the CONICA World Football Cup - a tournament for non-FIFA affiliated international teams.
The ref blew his whistle to halt play, showed the green card to a Padania player and ordered him to leave the pitch.
The ref appeared to make a ‘talking too much’ gesture with his hands. A graphic confirmed that the green carded player must be substituted.