Why do some stars appear to shine constantly white while the shining of others changes from white to blue and then red?

If the stars you are seeing are flashing blue then red before your eyes they are probably airplanes or helicopters.

However if you are seeing some stars that are red and other that are blue then the answer your looking for is here! :D

Like the sun these stars are giant balls of gas and the atoms have reacted with each other to eventually create stars. The stars radiate white light , the white light is notmatter or molecules and is only ENERGY. Imagine glowing energy, it is this energy that reaches the earth then into your eyes when the chemicals in the back of our head send the information to the brain ( the brain then translates the information into light)

White light consist of different energy waves the largest being Radio waves then micro waves, infra-red, ultra violet, x-rays and the smallest being gamma rays.

Now since these 'rays' have different individual wave lengths the wave length of the white light is stretched during the journey of reaching planet earth - you can detect in the visible light part of the electromagnetic spectrum radio waves that are the largest, are more close to the red part of the spectrum.- This is why stars appear red because the energy that they radiate are long and large as a result of them having to stretch to reach the earth- making their energy levels similar to the energy and heat levels of the red part of the visible light ,

and also similar to the colour that appears to us from where we are and the light's origination.

Blue appearing stars have the same light energy radiating from them and during their journey to earth the rays are more squashed -meaning more small wave lengths as the stars are closer to earth.

One of the smallest wave length is ultra violet , witch is closest to the purplish blue part of the visible lightfrom the electromagnetic spectrum making the light appear from where we are - blue.

Remember that it is not the actual ball of gas that is red or blue it is the light that we can actually see !

Another factor of the colour causing the red light is the temperature, if it is really bright and yellow/red - the temperature of the surface is red hot!

- angelbloom1424