■1. Layer Palette
I selected all of my flat color layers and set them to [Lock Transparent Pixel].
This means I can paint without going out of the flat color area.
▼ While selecting the layers you want to lock transparent pixels on, click this button on the [Layer] palette.
■2. Brush Settings
I used the following two brushes to paint.
・ Transparent watercolor brush
This is a default brush that you can find under [Brush] > [Watercolor] > [Transparent watercolor].
I adjust the opacity and color stretch as needed while I paint. I use this for light parts that I want to paint softly.
・ Customized transparent watercolor brush
When using watercolor brushes, the color can get darker and uneven when you go over already-painted areas.
I made this custom watercolor brush for when I don’t want the color to become uneven, even if I paint on top of a stroke.
I use this when I want to create clear shadows.
I customized the brush by selecting the [Transparent watercolor] brush and right-clicking to display the menu, then choosing [Create custom sub tool].
In the [Sub Tool Detail] palette, I went to the [Ink] tab and changed the blending mode to [Replace alpha].
Then, in the [Tool property] palette, I changed the [Hardness] indicator to the furthest left option (value: 1) to make it softer.
Under [Brush density] > [Brush density effect source settings], I unchecked [Pen pressure] so that the pen pressure does not affect the brush.
I used the brushes mentioned above to paint.
I made the base color a more blue tone, then first painted the shadows in one color before adding the lighter parts.
While painting, it’s important not to only use the same color or complementary colors, but also add some contrasting colors here and there.
This makes the image look more vibrant.
However, it can look messy if you add too many colors, so make sure you don’t shift too far away from your main colors.
Because the textures and gradient are layered on top, there’s a sense of cohesion despite the colorful tones.
 Painting the lights
Bright lights in the illustration draw the eye and add variation to the image.
I made a “lights” layer above my line art layers and roughly painted in the colors that I wanted to shine.
Painting in a gradient outwards creates a pretty effect.
To make it look softer, I blurred the “lights” layer.
I did this using the [Filter] menu > [Blur] > [Gaussian blur], with the [Area to blur] set at 80.0.
I set the blending mode of the “lights” layer to [Add], and adjusted the opacity so that the shape of the object is visible. In this case, the opacity was set to 61%.
By putting the “lights” layer above the line art and changing the blending mode, the lines also seem to glow and stand out more than other areas.
The following blending modes are good for expressing light.
・ Hard light
Note: For more details on layer blending modes, refer to the following TIPS.
I finished adding the light effects.
In the next part, I’ll show how I added reflections and bubbles to finish off the illustration.