# Do Background Colors Have an Impact on Preferences and Catch the Attention of Users?
## 3 Materials and Methods
** In order to find the most eye-catching and user-friendly color pairs, 72 images were prepared as follows: for each of the analyzed colors (black, gray, green, blue, violet, red, orange, yellow, and white), one color was fixed as primary (and set as a background), while the second color for each generated pictogram was chosen from the set of remaining colors and called the secondary color (set as a pictogram). Example images with a gray primary color are depicted in Figure 5. The images had an oblong shape in 1:2 proportions, which allowed for better fitting them to the display resolution. They took up 40% of the full screen surface. The object shapes were picked such that they did not distract the user. Hence, we chose a regular square shape and the widely known e-mail icon. However, colors, not shapes, were our primary focus. The choice of colors for the experiment is presented in the Figure 6.  
The experiment was conducted in 41 naive observers who were confirmed to have standard or corrected-to-standard vision. The age of the observers ranged from 25 to 60. For additional reliability, each observer repeated each experiment three times, but no two repetitions took place on the same day, in order to reduce the learning effect. According to [33], collecting 30-60 repetitions per condition is sufficient; where condition denotes two matched colors, represented by pictogram and background, in our context. The images were shown on a 50% gray background, which has been recommended by International Color Consortium (www.color.org, accessed on 15 October 2021) as a background for comparing colors. The same background was used for the intervals between displayed pairs of images. The mouse cursor was reset to a neutral position after each trial. The experiment was conducted on an EIZO ColorEdge CG220 22.2 inch display, calibrated using X-Rite i1 Publish Pro 2. For optimal eye tracking, the distance from the participant's eyes to the eye tracker was set at 60 cm, as recommended by [PERSON] [34]. In the room, constant and uniform lighting conditions were ensured through the use of lamps with color temperature 5000 K (D50 standard). According to the International Color Consortium, the color observation angle was 2\({}^{\circ}\). Additionally, surrounding light in the room was regularly controlled using a Sekonic L-478 DR light meter. For comparison, only images with the same primary color were displayed (see Figure 5). This enabled reliable comparisons by users, as introducing more than three colors (one primary and two secondary) would make the experiment difficult to conduct, or may even lead to inconsistent results. **Eye tracking metrics. ** The primary requirement of eye movement analysis, in the context of gaze-contingent system design, is the identification of fixations. Fixations naturally correspond to the desire to maintain one's gaze on an object of interest [35]. [PERSON] and [PERSON] (1998) [36] have reviewed past results, and indicated that the positions of fixations within a scene are non-random, with fixations clustering on informative scene regions. Fixations were considered the most suitable feature recorded by the eye tracker for our analysis. The main issue in the analysis of divided attention is to identify the areas where the user's eyes essentially stop scanning about the scene, holding the central foveal vision on the places that attract the user's attention most. In this research, our focus was to obtain an indication of the color composition that first attracts the attention of users. As the very first impression can be recognized by the first fixation, we used this in further analysis. The metrics were measured just after the pair of images was displayed and assigned to the color composition that first attracted the user's attention. To properly conduct eye tracking analysis, we defined two areas of interest that cover the displayed stimuli--AOI1 (the stimulus on the left) and AOI2 (the stimulus on the right)--with which the metric \"first fixation\" was computed.