The use of information and communication technology (ICT) devices has been spreading in many scenes in the daily life of elderly people, and a tablet computer has been considered as a useful tool to help them enhance their quality of life (QOL). In this study, we investigated how the colors displayed on a tablet screen affect the activation of the frontal lobe of elderly people while they are performing tasks on the tablet. Two experiments were conducted for concentration and memory tasks by using different display colors, and the oxygenated hemoglobin concentration changes in the brain region of elderly subjects were measured by near-infrared spectroscopy, which is a method of measuring the level of oxygenation in the blood flowing through the tissue with a near infrared light source and a light receiving sensor. The experimental results showed the following effects of display colors on the prefrontal cortex of elderly people: 1) green display color can enhance the activation of the prefrontal lobe, and 2) in the case of a simple task, the use of a display color with a high contrast ratio against black can induce the activation of the prefrontal lobe. These results can be utilized to improve ICT screen designs for elderly people to enhance their brain activation, which is closely related to the improvement of their QOL and sense of well-being.