# Automated Image-Based User Interface Color Theme Generation
## 4 Model Framework and Architecture
### Selecting Color Candidates
These differences are statistically significant (\(\chi^{2}(2)=18.383\); \(p<0.01\)) and confirmed by logistic regression (\(\chi^{2}(4)=48.73\); \(p<0.01\), Nagelkerke R\({}^{2}=0.13\)). According to coefficients, it is 2.6 times more likely that the analogous color theme will not be harmonious--compared to the themes where color harmony adjustment was turned off (\(p<0.01\)). Therefore, when using analogous color themes, the chances of achieving color harmony are lower than when color harmony adjustment is turned off. This finding implies that, rather surprisingly, the compatibility with the image is more important than the relationships of colors in establishing color harmony. While using monochromatic colors gives the highest probability of achieving color harmony, the most crucial factor is using colors compatible with the image. This indicates that color harmony also depends on the context, confirming the findings in previous studies [51]. It is surprising to note that the percentage of positive responses is higher for the light mode (89.9%) than for the dark mode (72.7%). The difference between the two modes is statistically significant (\(\chi^{2}(1)=28.633\); \(p<0.01\)) and has been confirmed through logistic regression analysis. Based on the obtained coefficients, it appears that colors are perceived 3.5 times less harmoniously in the dark mode than in the light mode. These findings align with previous studies, which found that harmonious color combinations tend to be lighter on average [23; 24]. ### Usability of Color Themes

#### 7.4.1 Visibility of Interactive Elements

In response to Question 4, participants answered affirmatively in 77% of all cases (\(\chi^{2}(1)=172.97\); \(p<0.01\)), indicating that colors used for interactive elements such as buttons are sufficient in contrast. The highest and lowest affirmative responses were achieved with Settings 1 (92.9%) and Settings 4 (61.1%), respectively. Analysis of responses while different settings were used revealed that the visibility of buttons did not statistically differ between light and dark mode (\(\chi^{2}(1)=2.54\); \(p=0.11\)),neither with different selection modes (\(\chi^{2}(1)=2.29\); \(p=0.13\)). In contrast, using different color harmony options led to statistically significant differences (\(\chi^{2}(2)=20.731\); \(p<0.01\)). The highest percentage of affirmative responses was observed when color harmony was turned off (84.4%). When color harmony adjustment was turned on, affirmative responses were lower; 74% for monochromatic and 65.5% for analogous options. The impact of the color harmony option was also confirmed by binary logistic regression (\(\chi^{2}(4)=24.76\); \(p<0.01\); Nagelkerke R\({}^{2}=0.06\)). According to the logistic model coefficients, it is 2.3 times more likely that buttons will not be sufficiently visible when the monochromatic option is used and 3.5 times more likely when the analogous option is set. It is surprising to note the effect of the color harmony setting on the visibility of buttons. When the analogous option is used, most buttons use the same tertiary color as when color harmony is turned off. The only difference is in the secondary color used for CTA buttons. Based on this, it can be inferred that due to the lower visibility of CTA buttons, some participants perceived the visibility of all buttons as insufficient. While button visibility could be improved by using more contrasting colors, doing so would likely compromise compatibility with the image. #### 7.4.2 CTA Button

Regarding Question 5, the results showed that 62.84% of participants answered positively (\(\chi^{2}(1)=39.03\); \(p<0.01\)), indicating that our model effectively chooses suitable color for the CTA button. Among all the settings, Settings 2 had the highest affirmative response rate (88.9%), while Settings 8 had the lowest rate (32.9%). Analysis of observed and expected frequencies using different settings indicates that all settings significantly influence the saliency of CTA button.