A good contrast of colors used in a user interface is crucial for a correct viewing by older adults, in particular older adults with visual acuity limitations. So in the user interface should be used a sufficient degree of contrast between the background and the foreground. One way to achieve this goal is using highly contrasting colors schemes, such as negative (light text on dark background) or positive (dark text on light background) polarities. Both polarities have similar levels of readability, but it has been noticed that negative polarity is slightly easier to read on the screen.