In preparation, I drew the outlines of the drawing with the pen tool.
Create a new layer underneath the lineart.
I choose the [Running color edge watercolor] brush from the [Watercolor] tools...
...and use a big brush size to fill the background with a light blue color.
Next, I paint the color of the skin on a newly created layer.
It's always good to make use of the zoom function in the [Navigator] palette
to focus on the part you want to fill.
By decreasing the pressure on your pen, adding color can be done lightly.
For this painting I will do both, changing the color by adjusting the pen pressure,
as well as changing it by picking up other colors.
Since there is a lot of transparency left in the image,
picking up the color from a layer with the eyedropper can't be done.
However, by switching the tool to [Pick up color from layer] the originally painted color can be chosen easily.
If you want to mix and blend the colors, it's best to use the blend tool.
While blending, the colors you are mixing will become increasingly blurred.
To draw the shadows for the clothes, I am adding a new layer and set its blending mode to [Multiply].
Then I paint the shadows, which can be done easily with a separate layer like this.
One way to add color that does not overflow the intended area,
is to create a selection with the [Selection] tool and paint inside of it.
Drawing the background is next.
I create a new layer and move it all the way down, underneath the color layers.
I select a blue to paint the sky and leave the parts for the clouds white.
Additionally, I'm going to select the layer with the lines to adjust their color.
To do that, I click the respective layer in the [Layer] palette and click the icon for [Lock tranparent pixels].
I use a darker red to paint over some parts of the lines with the brush tool,
for example in the face and on the hands
Textures can also easily be applied to the whole illustration if necessary.
I open the [Material] palette and choose an image material out of the [Monochromatic patterns]
and the [Texture] category to place on top ot the illustration and apply as a texture.
For this image I am going to drag and drop the material of a paper texture in.
After using the [Texture combine] function and lowering the strength of the texture,
I also lower the opacity in the [Layer] palette to give the whole image a paper-like texture.
Clip Studio Paint has many brushes and allows for a great variety of expressions.
Make sure to try them out to find what suits you best.
Also, there are more videos where I introduce manga drawing in monochrome and color and some useful features for that.
Check them out.