Changing the desktop background alone isn't enough. You will inevitably get into a situation where fullscreen windows are occluding it. To avoid any ambiguity,

Changing the desktop background alone isn't enough. You will inevitably get into a situation where fullscreen windows are occluding it. To avoid any ambiguity, set the color scheme to high contrast and then set all the windows title bars to red, and tint the task bar red. On QA, I tint everything purple, and on DR I tint everything green, or yellow.