Sony CUH-1116A Guide De Mise En Route page 14

Using multiple controllers
You can use up to 4 controllers at the same time.
When you press the (PS) button on a controller for which registration has
been completed, a colour will be assigned to that user and the light bar will
light up in their own colour, depending on the order in which they join in. The
first user is blue, the second is red, the third is green and the fourth is pink.
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