Open image you will use for banner, signature, header or some other purpose. I picked some image with nice looking girl for this tutorial. In Layers palette, double click on that (for now only) layer, and pop up will show up. Click OK and that way you'll make new layer of background. Create new layer. Set Foreground color to white. Pick Paint bucket tool and fill that layer. Move Layer1 bellow the Layer0. Click on Layer0 to make it active and set Opacity to 50%. Pick Rectangular Marquee tool and select part of image. I selected down part.
Right click and "Layer via copy".You just made Layer2. On Layers, double click on layer2 and on Layer style click Color overlay. Pick color you like (I picked green color), and set Opacity to 50%. You just made nice 2 color filtered image.