Yep, if a bright star is low down on the horizon you are looking at it through heaps of turbulent air. The air refracts the light and effectively gives you a varying degree of chromatic abberation and as a result the colour will change.
That is why you try to look at objects at least 30 degrees above the horizon if possible. The amount of air you are looking through is greatly reduced and so is its effect giving you a better, more stable image.
Cheers
BTW Welcome to IIS
