Dark side of the Moon.
Rachael... There is no difference in the meanings of the spellings other than 'Colour' is used more in European english speaking countries. It is also used more in Canada than in North America. However, there is no discernable difference in meaning. There is no inference of a more poetic nature of one over the other. There may have been some evolution in the entimology of the english language that caused a change from Colour to color, but they are one in the same in usage and pronunciation. I am not aware of any formal differences other than personal preference or habitual usage based upon cultural environment. My conclusion... they are one and the same, just spelled differently.
Welcome to P.I.P. I do hope you enjoy sharing here. People here will gladly render all the help and encouragement they can.... including me.
Once again, Welcome, Rachael.