I know it's not the case with all brands / watch lines, but I've noticed a trend. Blue is an attractive and soothing colour, and it seems manufacturers love to exploit this for premium models.
(1) Rolex Submariner:
Black SS, $9,000
Blue White Gold, $30,000. The price jump is justified by the use of white gold, but you can't get a current generation blue sub in SS.
(2) Omega Planet Ocean
Blue Ti ~ costs significantly more, supposedly Ti is the justification for the price bump although I doubt it costs that much more to make the watch out of Ti
(3) Christopher Ward Harrison ~ even the popular maker of British themed affordables is doing it.
Black - 312 pounds
Blue - 500 pounds. Aside from being limited edition, there's no material justification for the price jump.