People are using a "blue and red filter" on TikTok to duet with themselves.Luckily you don't need any third-party apps to get this effect — all you need is the TikTok app.First, Open the TikTok app and tap "+create" at the bottom of the screen.Then, Hit the "effects" option and locate the "trending" category.Lastly, Tap the icon and start recording your video — to switch between the red and blue lighting, blink your eyes.Musical fans and lip-syncers have embraced the "blue and red" filter as perfect for the In The Heights challenge and other duets
