“Our” Pearl originally belonged to White Diamond, and was made as a double agent. She was “gifted” to Pink to shatter her under White’s orders.
To do so, Pearl shapeshifted into the form of a Rose Quartz.
At the time, Pink Diamond was projecting Pink Light for some reason, just as Blue projected Blue Light in The Trial. This Pink Light saturated Pearl’s White skin and Peach hair with the color pink, giving the illusion more credibility.