Making picture like this two in photoshop is really simple.

The first one with multi-colored bubble was made by this way

1. open your picture
2. convert to black and white by layers (you can use "hue and saturation" or "black and white conversion" )
3. click to mask
4. select black brush and uncover color parts of picture. I used opacity about 50%-60% for uncovering bubble colors.





The second picture I made in Amsterdam Red light district in cloudy day and colors were boring except red signboards. So I used different way to make finnal picture.

1. open your picture
2. go to select menu a click on "color range", click "inverse", press shift and select color parts of your picture, click "ok"
3. convert to black and white by layer "hue and saturation" or "black and white"
4. you can make corrections by brushes

Tip: Set your cursors to "precise" mode. Press ctrl+k, select "cursors" in menu and click on "precise".