Labels and text inside Text Field becoming white automatically for iOS 13 Dark mode

if you are using System Color than it will automatically change in dark mode. so you can use Custom Color in Application.

Or you can set key User Interface Style and value Lightin Info.plist file.

Previously the default color of the UILabel was Black Color, but since iOS 13, the default value is LabelColor witch is a Semantic Color name from system UI Element Colors. To make it always black, change the color to black (not default). But be aware that the background color may change to black (from white) similarly.

Also you can eliminate the dark mode entirely by setting the UserInterfaceStyle on main window:

window!.overrideUserInterfaceStyle = .light

Note: Window where in AppDelegate until iOS 13, and now it is in SceneDelegate.

It's because your label's text color is set Default. In dark mode default color for text label is white and for view is black