517.160(A)(5) requires orange brown and yellow
with a distinctive colored stripe.
400.22(C) mentions light blue, but if is for jacketed cords furnished with an appliance - not field installed conductors.
424.35 is for lead wires on heating cables, these are likely to be factory installed and not field wiring.
504.80(C) is the only place I see with a color code for field installed wiring and it is an option, not a requirement according to how it is worded. If you want to use light blue for the purpose you can not use light blue for anything else.
I withdraw this statement:
The only colors for conductor identification that are mentioned in the NEC are white, gray, green, green with yellow stripes and orange for high leg delta systems.
And change it to:
The only colors for general use conductor identification that are mentioned in the NEC are white, gray, green, green with yellow stripes and orange for high leg delta systems.