# Enhancing Color Scales for Active Data Physicalizations
## 4 Color Evaluation for Data Physicalization
### Applying the Farnsworth-Munsell Test (FM)  
The pre-evaluation is a modified version of the FM color perception test for a physical and digital environment; i.e., the user must order a set of colors according to their perception from a starting color to a final color. In the original test, this is done with four sets (scenarios) of 25 colors. In this paper, the test will use four color sets with 8, 10 and 12 colors each. These color scenarios are selected at random and each scenario is shown separately. The main objective of the pre-evaluation is to compare the results of the tests carried out in the physical and digital environment, with the same sets of colors, in order to identify potential colors that can make up the physicalization of data. To this end, a physical artifact (bar chart) is built containing 12 bars, made using a modeling process (Autodesk Fusion 360 [59]) and 3D printing (3D Creality Ender-3 V2 [60]), and each bar is 10 cm high \(\times\) 1.5 wide \(\times\) 1.5 deep. These bars have an LED strip with 6 LEDs connected to an Arduino Mega board controlling the operation. The physical artifact is completed with interaction buttons for the bars (2 to 11), where the wiring diagram for the electronic components for dynamic color changes and button interactions are connected to a 5 (five) volt, 5 (five) amp power supply. The complete diagram is seen in Figure 5.  
The colors for the tests are generated using fixed color limits, then interpolated to generate each set in each condition. These limits are linearly interpolated on the HSV color space, and the codes below are given in RGB hexadecimal code. * Set 1--#B2766f, #9D8E48
* Set 2--#97914B, #529687
* Set 3--#4E9689, #7B84A3
* Set 4--#8484A3, #B37673  
Figure 4: Pipeline for proposing and evaluating color scales for data physicalization. It has three main modules: application of an adapted vision test, generation of color scales, and equipment setup. It ends with user evaluation using InfoVis tasks. Figure 5: Physical artifact with interaction buttons (**a**); electronic components connected to an Arduino Mega board (**b**); 10 cm height bar and 2 mm thickness front face of the bar (**c**). The limits are used to generate 24, 32, and 40 colors for the 8, 10, and 12 bars conditions, respectively. The colors of the limits themselves are not taken in this sum, as they repeat in each sequence. A total of 96 colors are generated. In each scenario for each condition, the colors are randomized using the Fisher-Yates shuffle. The color perception test was carried out with a group of 12 people who accepted the invitation and completed the FM test in the physical and digital environment. To select this group of users, the following requirements were established: to be over 18 (eighteen) years old, to have basic knowledge of reading data charts, specifically bar charts, and not to have problems differentiating colors (no form of color blindness). The digital scenario of the pre-evaluation test was performed on a desktop where participants viewed and interacted with the FM test on a digital display with the following characteristics: screen size 21.5, full HD, refresh rate 60 Hz, resolution 1920 \(\times\) 1080, LED. The digital interface presents each of the four sets of colors selected for testing and interaction with each pair of virtual buttons allowing two colors to be swapped positions. The scenarios are created randomly (Figure 6) and thus proceed with the task of reordering the set of colors. Each color set has a maximum of 12 colors, interpolated using the same method as the FM test, for a total of 48 colors. While the original test has more colors for each line, the objective is also broader. The evaluation presented will use the FM test technique in a quantity appropriate for visualizing the information (a maximum of 12 distinct discrete steps), not to confirm a form of color blindness.