A colorful Bokeh effect is, in fact, one of the most impressive special effects out there that at the same time is extremely easy to create, especially with Pixelmator.
Layers, the Gradient Tool and the Defocus effect are used in this tutorial.
Create a new image in Pixelmator. To achieve a result similar to the one shown in the tutorial, use a size of 1920×1200 pixels; however, feel free to use any other size as well.
Fill the background layer with a black color. Choose Edit > Fill, set Color to black and click OK.
In the Layers palette (View > Show Layers), click the Add button (+) to create a new layer. To create a blurry defocus for the image composition base, first double-click the Defocus effect in the Effects Browser (View > Show Effects Browser) and drag the sliders to set values approximately as follows: Size = 0.50, Blur = 0.30, Density = 0.59. Then set the Primary Color to white and the Secondary Color to black and click OK.
Please note that since the Defocus effect generates the effect randomly, your results may look different from the example in the image below.
Duplicate the recently created layer by choosing Layer > Duplicate. Set the duplicated layer’s Blending to Color Dodge, as the Color Dodge blending mode gives some depth to the circles.
In the Layers palette click the Add button (+) to create another new layer. Change its Blending to Screen.
To add small defocus circles to the recently created layer, select it and double-click the Defocus thumbnail again, then adjust the values to approximately: Time = 24, Size = 0.15, Blur = 0.03, Density = 0.75. Click OK.
Click the Add button (+) to create another new layer above the others. Set the Blending to Screen. To add medium-sized defocus circles to the layer, double-click the Defocus effect, and adjust the values to approximately: Time = 0.00, Size = 0.30, Blur = 0.1, Density = 0.55. Click OK.
In order to create a light blend between the circles, duplicate the recently created layer with the medium circles by choosing Layer > Duplicate, then change the duplicated layer’s Blending to Color Dodge.
In order to color the image, first click to add a new layer above the rest. Then click to select the Gradient Tool in the Tools palette; and, in the Gradients palette (View > Show Gradients), create your own gradient. You can also download the gradient that’s used in this tutorial here. Once the file is downloaded, double-click it and the gradient will appear in the Gradients palette.
Apply the gradient to the recently created layer and change its Blending to Overlay, since the Overlay blending mode combines layers equally. And the Bokeh effect is done!