The original image was taken in RAW format and intial processed by increasing the white balance temperature to bring out the colours in the sign. I quite like the overall effect this has had on the buildings too, but I wanted to London Underground sign to stand out more.
Using Photoshop Elements, I added a Hue/Saturation layer. I first masked the sign and then reduced the Hue setting to 32 and saturation down to 20. The next step was to add a levels layer, adjusting the shadow and midtones levels to slightly darken areas of the image.