Black and White and a Little Color

Here is a picture where, in post-processing, I only really liked two of the colors - the red and the blue on the structure in the foreground. (The rest of the colors in the picture were not really worth writing home about.)

So, I implemented a trick that I learned online: After I used Photomatix to create the first HDR image with the colors that I really liked, I went back and created a second image in black and white. I then opened up Photoshop (Elements 2 -- I know, Dark Ages...) and opened up the black and white image. I created a second layer and pasted the color image over top of the black and white image. Using the eraser tool, I took out all of the color... except for the red and the blue that I really liked in the first place. Here is the result: