OK, let's take for our example our shiny new Team Photoshop header graphic, and convert it a blue background based image.

With that image loaded in Photoshop, firstly we need to simply invert the image because we are going to be losing that white background and going for something a bit darker. So to invert the image, just select Image > Adjustments > Hue/Saturation (Or if you are using a PC, use the CTRL+I shortuct).

Now the image should take on a black background and the blues will look a bit pinky.

Next let's get on with altering the color of the image to find one to our liking, we are going to do this with the Hue/Saturation function, this can be found by going to: Image > Adjustments > Hue/Saturation (Or if you are using a PC, use the CTRL+U shortuct).

With the Hue/Saturation tool loaded up, firstly check the colorise box, as in this case we want to be changing all the color in the image, otherwise rather than just the shades, if you move the Hue/Saturation cross fade bars without this box checked you'll see what I mean... Now check it and move them... See... totally different effect.

So, how are you getting along... Found a combination that you like yet... For our blue forum template we chose this combination roughly equal to this: Hue 209, Saturation 50, Lightness +25. The blue was derived by mainly changing the hue to a color we were happy with, then adding some lightness to change the tone of the image.

Next we wanted to take the highlights are make them whiter, so the text stood out a little more. There are various ways to do this, but for this tutorial we'll be using Image > Adjustments > Replace Color.

First of all we need to select which color we want to replace and how accurate we want that replacement to be. So start off by selecting the 'eyedropper plus' icon in the color replace box, then hover over your image and select one of the light blue shades (like the text). Then just drag down the Saturation slider so it is about -75. You can play about with increasing lightness and adjusting fuzziness too, but for this example, and to help us retain the overall qaulity of the image we'll just be using the saturation function.

OK with that donw, you should have an image close to this: