Photoshop elements 9 editing colour problem

I've just encountered an unusual problem. When dragging photos from the project bin to the workplace and placing them on a blank sheet, my lovely colour pictures appear in black and white. I can only think I must have inadvertantly pressed some command somewhere, but what? and where? Please help me to get back to normal. By way of background I'm using Windows 10 on a Dell laptop, and have been performing this operation quite successfully for several years up to now!