The PS5 Dualsense controller features LED lights below the Touch Bar that appear to indicate the player number you are.
According to Japanese site 4gamer, which posted a series of images of the console and detailed some of its features, the new DualSense controller features four light bars on the left and right of the Touchpad along with four LED lights at the bottom. The light bar is said to glow in four different colours including blue, green, red, and purple, to indicate "when multiple controllers are connected to the PS5". Which light is showing also appears to correspond with which player number you are.
The #ps5 dualsense have 4 little lights bellow the touchpad, this appear to be to show you what player you are (1,2,3,4) pic.twitter.com/AOvbpKUO3BOctober 4, 2020
Interestingly, the article also says that the light is not that bright, "so you won't get distracted by it getting in your field of view." When it comes to the PS4 DualShock controller, you can often catch the glow of the light on the back of the controller reflected in the TV, which can be distracting at times. From the sounds of it, the DualSense's glow is more subtle, so it may be less distracting. Several images also appeared on Twitter showing the lights on the controller and how they appear to glow.
This PS5 controller feature came to light (pun intended) after Japanese YouTubers got to spend some hands-on time with the next-gen console this past weekend. Along with seeing some upcoming PS5 games such as Godfall, Astro's Playroom, and Devil May Cry 5: Special Edition running on the hardware, the hands-on also revealed that the PS5's cooling fans remain silent even after extended use.