## 1 Introduction
pointed out that yellow-on-black, yellow-on-blue, and white-on-blue backgrounds are the three clearest color combinations that can significantly improve the speed of visual search [14]. Furthermore, [PERSON] et al. recommended the use of blue and red characters on a white background for dark character/light background combinations and white characters on blue and green backgrounds for light character/dark background combinations [15]. [PERSON] et al. selected and examined the combinations of four foreground colors and four background colors and noted that in the design of icons for information interfaces, the use of six color schemes, namely white-with-black, yellow-with-black, turquoise-with-black, white-with-red, yellow-with-red, and white-with-purple, enhances icon search performance [16]. In summary, several studies have investigated the color of icons or text in digital interfaces, covering the subjective preference of individuals for color based on age, gender, etc., as well as the objective readability of text or icons with different color combinations. However, in practical interface design, the appropriate color of icons in the interface under different cognitive load scenarios is usually considered. In human-computer interaction-related research, the cognitive load of a task is an important concept, which is defined as the total amount of mental activity exerted on the cognitive system during task processing [17]. The cognitive load of different tasks usually varies, with tasks with larger cognitive loads requiring more mental activities such as attention, memory, judgment, and decision-making, whereas tasks with smaller cognitive loads are relatively simple and easy. For example, operations in high-stress environments such as military tasks entail high cognitive demands owing to their complexity. On the contrary, tasks such as phone bill recharging involve relatively low cognitive load. Cognitive load can arise from various factors, such as task form and complexity, time constraints, the uncertainty of outcomes, etc., each exerting different effects on human cognitive processes and task performance [18]; for example, too much time pressure may increase an individual's cognitive load to the point of decreasing task performance [19], while too little cognitive load can lead to diminished feelings of stress and drive [20]. As is well documented, excessive cognitive load limits an individual's attentional focus and task efficiency, thus impairing task performance. On the other hand, appropriate cognitive load enhances attention and efficiency, thus contributing to task completion [17]. The influence of cognitive load is complex. Empirical studies generally streamline the environment and the task to influence cognitive load only in specific ways. For instance, adjusting time pressure is a commonly employed method [21; 22]. Previous studies have investigated the effect of color on cognitive load under various conditions. For example, [PERSON] et al. examined the color of escape signs in the Zijingshan subway station and demonstrated that green and black colors lower cognitive loads and thus improve people's search efficiency [23]. [PERSON] et al. argued that cognitive load is not affected by the color and harmonicity of the dashboard [24]. [PERSON] assessed the effect of color combination patterns on mental load in computer work [25]. [PERSON] et al. investigated the effect of news text font style and font color on the cognitive load of intelligent user interfaces, and their results exposed that red keyword text significantly decreases readers' cognitive load under high introduced cognitive load, which in turn improves the efficiency of news reading [26]. Multiple studies have evinced that the red color affects task performance by impacting cognitive load [27]. [PERSON] and [PERSON]'s study performed a series of experiments from six perspectives and suggested that color selection should be based on the nature of the cognitive task.