And odds are if its all going into a common trench that the blue and orange are both telecommuncations cables of some sort. While orange is the typically used color, there is no mandate that has has to be any particular color for install, and for an install in common trench, color coding the cables is smart so you can figure out if you are working on the right one...
Now if those cables need to be marked, they are all marked using orange paint and flags, regardless of the actual cable color.