Colour Bubbles
ONE. Heres the image I'm going to add 2 colour bubble to :
TWO. Now, use the paint brush tool,
, and change your settings to : 
You can change the size depending on the size of you image, 100 - 300px normaly look the best. With the colours blue, white or pink normally look the nicest, but you can use different colours depening on which suit your image.
THREE. Just make a new raster layer and set it to screen at 100%, then just add your bubbles on, I've added 2, here's my image :
FOUR. Now dupliate your base image and drag it to the top and set it to overlay at 100%. Your layers pallet should look like this :
FIVE. Then your done! This is my finished result!
Tutorial by oh-vintage.co.uk