They reflect all the light and don't let anything through. The pigment density in paints with this feature is much higher than the others. When you apply an opaque color on white paper, you cannot see the paper.

When referring to a hardware device or software program, opaque can mean more than one thing. It can mean not passing any information in the device or program, or in the device or program that processes the information.

What is Layer Opacity?

Opacity opens in two places: Layer Opacity and Brush Opacity.

- Layer Opacity is pretty simple; the Layers panel adjusts how visible or invisible the selected layer is.

At 0%, a layer is completely transparent; It is completely opaque at 100%. All values in the middle represent a sliding scale.

- Brush Opacity is best understood with Brush Flow. Both are controlled from the toolbar when you select it.

For each brushstroke, Opacity controls the transparency of the paint you apply, while Flow controls the speed at which it is applied. No matter how many times you paint the same area with one brush stroke, no more paint will be applied than the Opacity level. However, when the Flow is less than 100%, the painting effect occurs the more you paint over an area.

Opacity and Flow have their uses depending on what you want to do. Opacity is most useful for setting a hard limit on how much paint you want to transfer, while Flow is best for letting you build effects gradually.

For example, if you're running and burning, it's best to use Flow to control how much paint is applied, as you can add more by repainting the area with the same brush stroke. If you use opacity, you are more likely to give your work unnatural hard edges.

For more information about design and colors; https://cinema8.com/blog/visual-design-principles