What is a good opacity for illustration?

The opacity you choose for your illustrations depends on various factors, including the style you're aiming for, the medium you're working with, and the effect you want to achieve. Here's a general guideline:

Solid Colors: If you want solid, vibrant colors with no transparency, use 100% opacity.

Transparency for Layering: For layering elements and creating depth, a lower opacity (around 20-40%) can be effective. This allows underlying layers to show through slightly, giving your illustration more depth.

Blending and Softening: When blending colors or softening edges, you might use a slightly higher opacity (around 50-70%) to maintain some transparency while still covering underlying colors.

Highlights and Shadows: Opacity can be varied to create highlights and shadows. Lower opacity for highlights and higher opacity for shadows can give a realistic effect.

Textures and Patterns: Opacity can be adjusted to control the visibility of textures or patterns overlaid on your illustration. It's often best to experiment with different opacities to see what works best for the effect you want.

Remember, there are no hard and fast rules. It often comes down to personal preference and the specific requirements of your illustration. Experimenting with different opacities can lead to interesting results and help you develop your own unique style.