A quick guide to using the Colour Replace Tool.

1. Load the image that you want to perform the change on.
2. Go to Image>Adjustments>Replace Colour to bring up the Replace Colour dialog box. Click on the area of colour you want to replace - you will see it turn white in the dialog box thumbnail -

3. Move the Hue slider to the right or left a bit so you can see a colour change on your image - this is only for reference and will help you select the remainder of the colour to be changed -

4. Now, hold down Shift and click on the remaining colour to be changed. You will see more white added to the thumbnail and the colour will change in your image as you do this. Keep going until you have selected all the colour to be changed, use the thumbnail for reference -

5. You can now use the Hue, Saturation and Lightness sliders to adjust the colour to the one you require -

6. With a bit of playing around with the sliders you can match the colour to another building etc.

This is a very basic technique but a handy one to know.