When you paint the Bokeh layers, set that group to 'color dodge' and have that group layer above the color. Then below the bokeh layers, make a layer that has the color gradient. Set the gradient to 'color overlay' and you should have it. Oh, and make the background a gray-ish color.
Lovely, was this digitally rendered I'd assume? I don't think I've ever seen bokeh have outlines. It's a good, kinda cartoony representation, and the wallpaper is very pretty, It's become my new wallpaper, and I'm adding it to a wallpaper collection. Great job.