IB-5 pickups...how to tell the difference

[McCreed]

The wiring diagram for the IB-5 shows red covered wires from the bridge pickup, and yellow from the neck. Could that be it?

Unfortunately the wire colours vary greatly between PBG diagrams and the wire colour that ends up on the pickups.
It seems to be more about what colours they have on hand at the factory on any given day.

If you have a multimeter, there may be a measurable difference in the pickups DC Resistance (DCR). Typically the higher DCR will be the bridge pickup, the lower for the neck pickup.

Edit to add:
If you don't have a multimeter, and you plan on doing more kit builds or mods on your other guitars, they are a vital part of your tool kit.
You'll also find you will use it for lots of non-guitar jobs (like testing batteries). You can spend as little as $10 (not recommended) to $100+
but somewhere in middle ($30-$60) is fine for what most us do here.

If you live in AUS, Jaycar is just one many electronics suppliers that carry Digital Multimeters (CLICK)