[1] Changing the line art color

I change the line art layer opacity to 100% and adjust the colors with [Edit] menu > [Tonal Correction] > [Hue/Saturation/Luminosity].

 

The lines were blue, but I decided to change them to a redder tone to soften the color.

 

[2] Extracting the neon lights from the colors layer

I’ll add a blur effect to the neon lights in the illustration.

 

First of all, I duplicate the colors layer.

 

I name the duplicated layer as “soft blur” and place it above the “colors” layer.

Note: When you duplicate a layer with [Lock Transparent Pixel] enabled, the duplicated layer will also inherit the same settings. I don't want to lock transparent pixels on the new layer, so I uncheck the option.

 

I click only the neon light parts using the [Auto select] tool to create a group of selection areas.

 

If you want to select multiple areas, press the [Shift] key while you click to add selection areas.

 

After I’ve selected the neon parts, I go to the [Selection area] menu > [Invert selected area] to invert the selection area, and delete everything other than the neon lights by pressing the [Delete] key.

Only the neon parts remain on this layer.

Note: In the upper figure, I am hiding the original “colors” layer for clarity’s sake.

 

[3] Blurring

In order to express the glow of the neon lights, I blur the “soft blur” layer.

 

I select the [Filter] menu > [Blur] > [Gaussian blur] and set the “Area to blur” to 100.

Note: Since the value of the blur area also depends on the illustration, check the preview to find the best setting for each case.

 

After blurring, I set the layer opacity to around 50% to add a sense of transparency.

If the effect seems weak, I duplicate the “soft blur" layer and place it above the line art layer so that it looks stronger.

 

Here, I lowered the opacity to 20%.

 

The illustration now looks like this.

 

In the final part, I will use gradient and textures to finish the illustration.