Based on the basic instructions of reference layers, we will introduce a few practical methods for using it more conveniently.
* Refer to the following article for basic guides on how to use reference layers, etc.
 Coloring vector layer line art
Since you cannot fill in vector layers with color, use a different layer for this.
When doing this, set the vector layer with the line art as the reference layer to make it easier to color.
 Utilizing the “Not refer editing layer” for the [Fill] tool
■ 1. Coloring without added layers
Use a reference layer and the “Not refer editing layer” setting of the [Fill] tool to color on a single layer.
① Paint the coloring layer using the [Pen] Tool. Do not worry even if color escapes the line art. The tips of hair often have unpainted parts, so it’s OK to let the color flow outside the lines.
② Set the “Line art” layer as reference layer.
③ While setting the [Multiple referring] of the [Fill] tool to [Reference layer], set the “non-reference layer” to [Not refer editing layer].
④ Select the “Coloring” layer and use the [Fill] tool to paint.
This ignores the “Hair and skin” layer already filled with the hair’s color, and only refers the [Reference layer] while filling. Therefore, the color of the hair overlapping with the face is filled with the skin color.
If the non-reference layer is not set to [Not refer editing layer], it will be as follows.
⑤ Add color to the other parts in the same way.
The “Coloring” layer looks like this now.
* 2. Delete the color outside the line art
The image created in 1. has colors outside the line art of the character. You can delete these parts using the reference layer.
Select the “Coloring” layer and set the drawing color of the [Fill] tool to “Transparent color” before filling the outside of the line art to delete the color of the part that are outside the line art.
The advantages of not referring to the coloring/editing layer is that the colors can overflow the line art. Since you can draw without thinking about the boundaries of the lines, you can paint while maintaining the momentum of the brush.
This illustration uses anime-painting for the sake of clarity, but it is useful when adding gloss to hair or adding shadows to clothes as well.
If [Not refer editing layer] is inactive, you cannot unnecessary color fills successfully in the following cases.
① You cannot delete parts without any type of drawn content.
② Edges of the drawn colors may remain if anti-aliasing is applied.
③ You cannot delete colors at once if the drawing area is divided by line art.
Only the line art is referenced if [Not refer editing layer] is turned on, so anti-aliased edges will not remain, and divided color regions can be deleted at once.
 Referring to a plain
The reference layer can also refer to a “plain” instead of a “line”.
Let’s add color to this image without any line art in the following way.
① Set the “Flower” layer as reference layer, and use the air brush to add color to the color layer.
② Set the [Fill] tool to “Transparent color” and apply the following settings on the [Tool Property] palette.
[Area scaling] → off, [Multiple referring] → “Reference layer”, [Non-reference layer] → “Not refer editing layer”
③ Fill the “Coloring” layer.