https://learn.microsoft.com/en-us/dotnet/api/system.drawing.systemcolors.gradientinactivecaption?view=netframework-4.8.1&viewFallbackFrom=net-9.0
SystemColors.GradientInactiveCaption Property (System.Drawing) | Microsoft Learn
Gets a Color structure that is the lightest color in the color gradient of an inactive window's title bar.
property systemdrawingmicrosoftlearn