If you are referring to the orange light with the engine symbol in it - means there is a problem with the engine management system - could be something simple such as a loose connection or a faulty sensor - you will probably need the problem diagnosed properly, Ie. take it to a dealer or a mechanic with the proper diagnostic equipment.
is it the ; oil light, battery/charging light, brake wear indicator light, or some other one? different reasons for different lights.
red ones serious!
orange ones warnings, but not so urgent.
My dad has had loads of problems with his Vectra engine light coming on. He has taken it to the garage loads of times and they have never found a problem with it.