The goal of this research was to provide a set of criteria for the effective use of color on the IBM 5153 Color Display. Available guidelines provide direction but not the detail required for application programmers. This study examined character legibility and subjective preference for color combinations in text in an application program. The effectiveness of color combinations was defined as a joint function of response time and subjective rating. The graphs of foreground/background color relationships show the observers' performance as a function of their preference. The results indicated the flexibility of black or blue backgrounds. The findings are discussed with respect to principles of human perception.