In this article, I’ll show you how to change the original bland illustration on the right to a city pop style illustration.

〇 background

Many illustrations with a city pop style have a sky illustrated in the background.
The background should be a gradation of blue and light blue embodying the sky.

As for color saturation and lightness/darkness, saturation can be seen from low to high.
Unless it’s nighttime, it’s best not to use too much of dark colors in city pop illustrations.

For here, I’ll use a low saturation shade.

 

〇 cassettes

City pop style illustrations have a feeling of using a variety of colors such as white, pink, blue, yellow, and green.
Color the cassette in a bright green.

 

〇 hands

I think the reddish tint of human skin color is one of the characteristics of city pop illustrations.
Color it pink.

Color the shadow also in pink.

 

〇 reflected light

We will add a reflection of yellow light to express the vibrancy.

 

〇 effect

The orange color will be added to the line as an effect.

 

〇 frame

Color the frame from black to blue to blend in with the background

And it’s finished. 
What do you think?
I think there are many different ways to express the city pop style in illustrations, not just the coloring introduced here.
I encourage you to search for your own favorite artstyle!