There is a lot of research from the fields of Ergonomics and Human Factors (the study of the relationship between humans and their work environment) that shows that the preferred color combinations for maximum readability is a dark text on a light background. My own preference is usually black on gray. The gray background is easy on the eye and does not cause fatigue as readily as pure white. The black text maximizes contrast, which is good for readability.
If you use color in the text, you should use it sparingly and with intent. That is, color should not be used for show but to emphasize a point or to convey information. In Western cultures, we usually associate red with danger, green with moving ahead, and so on. Red can also be hot and blue cold. Other cultures have different interpretations of color so you have to be careful if planning a cross-cultural product.
There are some items to remember with respect to color. First, about 10 percent of adult males in the United States are color deficient. That is, they have difficulty seeing or differentiating some colors. The most common difficulties are associated with red and green. My father, for example, has always stated that if traffic lights were suddenly changed to have red at the bottom, he would drive straight through because he does not see the red and the green but merely knows which light is illuminated.
Second, some colors do not go well together. Try putting red text on a rich blue background or vice versa. You may have extreme difficulty in reading what is there. There are many Web sites that use color badly. Try to find some and share them with the rest of the class.