Photographer Amanda Cross, of Lancashire in the United Kingdom, wrote:
I wanted to compare the colors of different stars next to each other. These are stacks of Rigel, Betelgeuse and Sirius. I took individual images 60 seconds apart with iso 16000 and speed 1/50, stacked them with starstax and presented them together to show the different colors of the stars. I took the images deliberately out of focus to show the colors.
The color variations between Rigel and Betelgeuse are due to these stars’ true colors. Rigel is a blue-white star, and Betelgeuse is a somber red. The colors of Sirius, on the other hand, are likely due to Earth’s atmosphere. If you see Sirius high in the sky, it shines with a white color. But if you catch it low in the sky (as you would often catch it, from the U.K.), you’d see it sparkle in many different colors. Those colors of Sirius are from the greater thickness of Earth’s atmosphere in the direction to any horizon. The atmosphere splits the light of stars, and the camera picks up the colors.
Bottom line: Photo comparing colors of stars Rigel, Betelgeuse and Sirius.