Input (grade 13): If it is necessary to use colors, try to choose colors that are unambiguous (such as orange and violet) when viewed by a person with red-green color blindness (the most common type).
Output (grade 8): If it is necessary to use colors, try to choose colors that will not be confusing to a person with red-green color blindness (the most common type). Colors that are okay to use include orange and violet.