Duplicate the Background layer. On the new layer go to Filter > Blur > Gaussian Blur. Enter 10 for the radius. Hit OK. Set the layer’s blending mode to color. Double-click on the layer to the right of the name to open the blending options. Under Advanced Blending, uncheck the R and the G. This makes the layer only affect the blue channel no matter what we do to it. Now go back and check out the blue channel. Looks better.