Open a new file -- set the dimensions to 24 x 24 pixels.
Click 'New Layer' in the Layers palette, and fill half of the layer with black.
Turn OFF the background layer. (We want our pattern to be transparent)
Select Edit > Define Pattern, and give it a name.
This pattern will now be available to your work file. You can close the pattern work file or save it to modify in the event you don't like it and need a different one.
Now return to your work file, click a new layer, and select
Edit > Fill > Pattern, and select the new pattern you just created.
It will now fill the blank layer.
Setting The Monochromatic Color Layer
Next we'll colorize the image using a new blank layer, filled with the blue color. Set that layer in the Layer Blending Modes to "Multiply"
Adjust the Opacity slider for that layer until you like what you see.
Now, adjust the Opacity slider for the Pattern layer until a bit of the image appears through the stripes.
Make a copy of your Pattern Layer. (You may not like what I'm going to do next!)
With the Pattern Layer selected, choose the
Filter menu > Blur > Gaussian Blur and add some blur to the stripes.
Experiment with the blue and remember you can always 'undo' the action if you don't like the results. (Open this diagram)