That is Chromatic aberration..
Longitudinal and lateral chromatic
aberration of a lens is seen as "fringes" of color around the image, because each color in the
optical spectrum cannot be focused at a single common point on the optical axis.
Since the
focal length f of a lens is dependent on the refractive index
n, different wavelengths of light will be focused on different positions. Chromatic aberration can be both
longitudinal, in that different wavelengths are focused at a different distance from the lens; and
transverse or
lateral, in that different wavelengths are focused at different positions in the focal plane (because the
magnification of the lens also varies with wavelength).
Go to Wikipedia for a fuller explanation. Hope that answers your question.
My 2 cents worth: I like the composition but:
1) Image is out of focus
2) Not a good candidate for selective colouring.
3) and observation: Periodically clean the dust off your lens (it is showing up on the image as tiny white spots.)