Astronomers often refer to the colour of a star, which seems a bit odd because we mostly see stars as white twinkly objects. However, even with the naked eye, we can look closely at certain stars and detect a hint of colour – just look at this image of the Orion constellation. As we view him, the left shoulder has a red coloured star, while the right shoulder and right foot appear to be blue.
image: Orion 3008 huge.jpg, Wikipedia
Now click on the image to see the same view at much higher resolution. In the hi-res photo, look at the stars in the background. They’re not all white!
What can the colour of a star tell us?