text: The stars are different colours not only due to there size and mass, but due to an effect called the Doppler shift. Also remember what Einstein said, "It is all relative to the observer". A Red giant to us, would be a blue giant if viewed from a different angle elsewhere in the Universe. Now my question to you is, Where in the Universe would you have to be to see this Blue Giant? As to the colour temperature of the sun, take a Bunsen burner or propane burner that you find in any school lab class and play with the air fuel ratio and watch the colour of the flame change. If the ratio of gases that cause our sun to burn changes, it will effect the colour temperature in which it burns. Remember there is more to the universe than what the eye thinks it sees. I hope this answers your question.