Value
Value Perception
Value is the term for the relative lightness or darkness of a color. Humans tend to have difficulty comparing values that are not right next to each other. They struggle when trying to deterine if a value is darker or lighter than another. Take a look at the image below.
Which is darker, square A or B?
B does seem lighter does it? It appears so because it is surrounded by darker values. The values surrounding a color often influence our perception. In reality both squares are the same value.