You will need some white cardstock, 2-3 water based stamp pads, 1 pigment white based ink pads, sponge daubers for each color and a template of different sized circles made out of cardstock.
You use the sponge daubers to make circles of ink on your white paper. After you complete this, you will take the circle template and the white pigment ink and make white circles randomly on the colored ink. This will get the "out of focus look". Below is an example of what one of mine looked like this weekend. You can see my circles of color, as well as the white circles. You could use the template for all the colors if you wanted them all to be perfect circles. I used 1 1/4" and 1" circles for this.
I used this technique along with our Taste of Summer paper pack to make mothers day cards. Below is a finished card.
I also did a you tube video on this technique which can be found here:
Bokeh Technique-NikkiD's You Tube Channel