Being the Playstation fan and overall gamer, I’ve always liked the Playstation controller, it felt right and once they added the analog sticks, it got close to perfection, although, I don’t like how the L2/R2 button feels on the PS3. Anyways, Teiyu Goto, who was one of the lead designers of the Playstation, has revealed what his initial ideas of using shapes and colors were meant to be. This is what he said:
“Other game companies at the time assigned alphabet letters or colors to the buttons. We wanted something simple to remember, which is why we went with icons or symbols, and I came up with the triangle-circle-X-square combination immediately afterward. I gave each symbol a meaning and a color. The triangle refers to viewpoint; I had it represent one’s head or direction and made it green. Square refers to a piece of paper; I had it represent menus or documents and made it pink. The circle and X represent ‘yes’ or ‘no’ decision-making and I made them red and blue respectively. People thought those colors were mixed up, and I had to reinforce to management that that’s what I wanted. “
As far as I remember, these buttons initially were configured to do these over in Japan but for some reason when the Playstation came over to the US, X became the “X-cept” button and some RPG’s had the Triangle button as the menu button. Of course, later on we were introduce to the button configuration option which led us to have whatever button to do what we wanted and now games have it set to whatever works.
Source: Unreality Magazine