The sky does change with the angle you look at it. Even on a clear day with a cloudless sky, it will always look whiter and milkier the further down towards the horizon you look/point your camera, and always the bluest, the higher up you look/point your camera. And to me it always seems as if the camera sees the whiter bits even clearer than my eyes do, since my brain seems to add some blue to it from my memory...
Other than that you can take influence on the sky colour yourself by exposure. Ever since I have lost my polarizer somewhere where it was impossible to find it again (maybe some future archaeologists will, but I didn't :cry: ), I have tried to enhance the blue by deliberately underexposing ... if I, however, expose only a 0.3 stop differently, the sky will look different. So yes, both speed and aperture may give you different results in so far as they can both lead to "normal exposure" (which I take as overexposure in my camera's default settings, mind), or over and underexposure.
The white balance your camera is set to may have an influence in the way your sky looks, of course, though as long as it is set to "automatic", the camera should choose "daylight" for its white balance all by itself.
Show us some examples, will you? Those might make answering your question a lot easier.