# Enhancing Color Scales for Active Data Physicalizations
## 4 Color Evaluation for Data Physicalization
### User Tests
#### 4.8.3 InfoVis Tasks  
The InfoVis tasks defined to evaluate and compare color palettes include identifying individual colors, grouping colors, reading color coding, finding maximum and minimum color codes, and ordering a set of colors. All tasks end with a button press, indicating the bar that was the target of the task or the number of elements for the task. Tasks are described below:  
1. Identify unique color coding: * Identify the unique color (Figure 17a). In more detail, Figure 17a presents a random scenario generated by an algorithm that specifies the occurrence of a unique color (just one). In this example, the unique color is shown in bar number 4. * Consider bar number 12 as a target color. Identify the number of occurrences of it (Figure 17b).
2. Identify the number of different color groups:* Identify the number of different color groups in the physicalization (Figure 18).
* Identify color-coded values:
* Identify which bar represents the categorical color value indicated at bar number 12 (Figure 19a).
* In a sequential color scale, identify which bar corresponds to the color indicated at bar number 12 (Figure 19b).
* In a divergent color scale, identify which bar number corresponds to the color indicated at bar number 12 (Figure 19c).  
The scenario presented in Figure 19 is to locate a target color. The target color is displayed in bar number 12. The difference between scenarios (a), (b), and (c) is that the first one uses a categorical color palette, the second one uses a sequential color palette, and the third uses a divergent color palette.  
Figure 19: The InfoVis task of identifying color-coded values: (**a**) identify the categorical value indicated in bar 12; (**b**) identify on a sequential scale the color indicated in bar 12; (**c**) identify on a divergent scale the color indicated in bar 12.  
Figure 17: Examples of scenarios with a categorical color palette: (**a**) identify the unique color; (**b**) identify the number of times the target color occurs.  
4. Find maximum and minimum color-coded values: * Consider a sequential color scale, and identify which bar is the maximum value (Figure 20a). * Consider a sequential color scale, and identify which bar is the minimum value (Figure 20b). * Consider a divergent color scale composed of two primary colors (yellow and blue). Identify which bar is the maximum value (darker blue) (Figure 20c). * Consider a divergent color scale composed of two primary colors (yellow and blue). Identify which bar is the minimum value (darker yellow) (Figure 20d). * Compare color-coded quantitative values: For the first two tasks in this section, lighter colors represent lower values, and darker colors represent higher values, and the last two are reversed. * Consider a disordered sequential color scale. Identify which bar has the highest value (Figure 21a). * Consider a disordered sequential color scale. Identify which bar has the lowest value (Figure 21b). * Consider a divergent color scale composed of two primary colors (yellow and blue). Identify which bar has the highest value (Figure 21c). * Consider a divergent color scale composed of two primary colors (yellow and blue). Identify which bar has the lowest value (Figure 21d). The scenarios presented in Figure 21 enable a user to compare two colors that represent values of a scale to identify which represents the highest or lowest value. These target colors are located in bar number 1 and bar number 12 and are generated randomly. The bars numbered 2 to 10 represent the color palettes proposed, which can be sequential, like (a) and (b), or divergent, like (c) and (d). In this case, the number 11 bar does not display any color.  
Figure 20: The InfoVis task of finding coded maxima and minima: (**a**) identify in a sequential scale the maximum value (darker colors); (**b**) identify on a sequential scale the minimum value (lighter colors); (**c**) identify the maximum value on a divergent scale (blue plus dark); (**d**) identify the minimum value on a divergent scale (dark yellow).