Why did Windows 7 log on slower for months if you had a solid color background?

Personally, I use a solid color background. It was the default in Windows 95,¹ and I’ve stuck with that bluish-green background color ever since. It’s sort of like my comfort food. Imagine my surprise when someone pointed me to a support article titled “The Welcome screen may be displayed for 30 seconds during the logon process after you set a solid color as the desktop background in Windows 7 or in Windows Server 2008 R2.” Why is logon slower with a solid background? After your logon has been authenticated, Windows sets up your desktop. There are a lot of things going on. The taskbar gets created. The components that are responsible for various system services are loaded and initialized. The desktop window is created and filled with icons. And the desktop background window loads up the desktop wallpaper and paints it to the screen. The logon system waits for all of these pieces to report that they are ready, and when the all-clear signal is received from everybody, or when 30 secon ... Read full article.