That background either matches the system theme or pulls from the theme of the app. In some cases, like Google Chrome, this splash screen is brand new in Android 12 and not a part of the app itself.

When any app opens in Android 12, the user will see a new app launch animation, "a splash screen showing the app icon, and a transition to the app itself." This will be standard and by-default for ...

The screen features the WhatsApp logo with a white background. WABetaInfo reported that the Splash Screen was first spotted on WhatsApp Business beta in the iOS 2.19.110.21.