Don’t rely on color alone to carry meaning. If your syllabus says that all red assignments will be due by week 6, you may leave out people with red/green color blindness or people who use screen readers and can’t tell which words appear in red. It’s OK to use color that way as long as you also distinguish those items in another way. Precede each with "Due week 6," for example.
Also, make sure you have good contrast between text and background. Dark text on a light background is best. A lot of people have trouble distinguishing between red and green and may not see red text if it’s on a green background. If you have doubts about your page’s contrast, print it in black and white to see if you can read everything easily without the color.