The message would be:

The color scheme has been changed

The reasons could be: • Your laptop might have switched from Mains Power to Battery Power. • A program that you are presently running maybe incompatible with Aero and hence some visual element must have automatically got turned off. Windows will automatically change the theme back to Aero when such programs are closed. • Your computer may be low on memory and may not have enough memory to run all your open programs and Aero themes. • The hardware configuration or screen resolution of your computer may have changed. If the minimum hardware requirements are not met it may not run Aero themes. The change is usually temporary and on rectifying or reversing the above, your computer will revert back to using the visual aero elements. In case it doesn’t, then you may want to use enable Aero back manually or use the  Aero Troubleshooter.