I created this power point presentation to help my students understand how to classify stars. This powerpoint includes the differentiation between star colors, absolute and apparent magnitude, the HR diagram as well as how data is collected. Although it's short, its a great into to the concept.
Make sure to check out the rest of my Astronomy resources: http://www.teacherspayteachers.com/Store/Mrs-Kendall/Category/Astronomy
(astronomy, stars, star classification, power point, lecture, notes, science, Hertzsprung Russell Diagram)