1. Causes of Variation in Color Response Color perception has been shown to be affected by psycho-physical factors: Colors are perceived differently according to the surrounding context Psychological factors affect visual memory memory color: Psychological factors affect visual accuracy 2. Effects of Color on User Tasks Color responses affect how well users can perform tasks Discrimination and search studies Finding an item is fastest if Search time is not affected by Search time increases if Tracking studies Tracking a moving item is fastest if Slowest if Personality type affects value of color for recognition 3. Guidelines for Color Use Based on Psychological Factors See color guideline Web pages for more info (1) Vary color along more than one dimension to maximize discrimination. (2) Avoid subtle distinctions in color. (3) Juxtapose different colors to be compared, particularly similar ones. (4) As the number of colors increases, increase the size of small images. (5) Font and line width are at least as important as color in establishing legibility. 4. Using Colors as Codes Color coding enhances display capabilities Uses of color coding discrimination/recognition: quantitative differentiation: qualitative differentiation: indicate characteristics Examples of color coding schemes Four "psychological primaries" (focal colors) False coding: Overloaded colors: Redundant cues: Cultural effects of color stereotypes [Courtney, 1986] 5. Guidelines for Color Use Based on Cognitive Factors See color guideline Web pages Read these on your own; we won't have time to go over them again (1) Use color sparingly. (2) Use the four "focal colors" to encode information that needs to be remembered. (3) Minimize the amount of coding the user is expected to learn and re-learn. (4) "False coding" will confuse and frustrate users. (5) "Overloaded colors" will confuse and frustrate users. (6) Color use must be meaningful and consistent to facilitate searching or tracking. (7) Provide labels or legends with colors when the meaning is not obvious or when several meanings must be remembered. (8) Use names, rather than numbers, to describe colors. (9) Use redundant cues to augment color coding. (10) Where possible, match hues with conditions or actions being represented.