I've never seen any difference in the colours or understood why Sciences and Medical would need to be identified by separate colours. The likes of Security and Engineering/Operations however, since they are very different disciplines, would make more sense for a little colour differentiation. To me anyway.didn't at some point they use turquoise for science and blue strictly for medical in TNG?
Security and engineering do receive similar training. After all, that is the only way it could have been possible for Jellico to reassign half the engineering staff to security as soon as he took over the Enterprise.