Final answer:
The edges indicating visual distance between colors are defined by contrast and shading, which helps to create depth perception. Techniques such as hatching and the use of analogous and complementary colors enhance this effect.
Step-by-step explanation:
The type of edges that indicate visual distance between parent colors is related to the way our eyes perceive contrast and shading in color. Edges play a significant role in how we interpret depth and the placement of objects in space. For instance, adjacent colors on the color wheel, known as analogous colors, tend to blend smoothly and might not create a strong sense of depth. However, when an edge occurs between colors of different hues or saturation, such as a light area against a dark one, our perception of depth is enhanced. This is partly due to the processing of nerve impulses in the eye, affected by the interaction of light receptors, specifically rods for night and peripheral vision and cones for central vision and color.
Furthermore, techniques like hatching, where closely spaced lines create shading, help to give a sense of form and depth to an object. When an artist uses complementary colors, such as the green against the red described in the Essex and Hester painting, there is a sensation of vibration, which can also suggest depth. Colors and how they are applied, whether sharply defined edges or smooth transitions, contribute to the perception of distance and dimension in art.