Let's break down the situation and the best practices

Understanding the Importance of Phasing
Safety

Consistent phasing is crucial for safety. Imagine someone working on a circuit downstream and assuming the phasing is consistent only to find out it isn't. This can lead to unexpected voltage differences and potential shock hazards.

Troubleshooting

Standardized phasing makes troubleshooting significantly easier. If things aren't working correctly, knowing the expected phase color on each wire is invaluable.

Preventing Incorrect Connections

Although less critical with lighting, incorrect phasing can be a bigger issue with motors or other 3-phase equipment. It's a good habit to maintain consistent phasing throughout the system.

Best Practices for Your Scenario

While not strictly required in your case, it is highly recommended to maintain consistent phasing through the contactor. Here's why:1. Continuity of Identification

The original panelboard circuits are identified by their phase colors (Black, Red, Blue). By maintaining that identification through the contactor and out to the lighting circuits, you're preserving the original intent of the installation.2.

Future Maintenance

Down the road, if someone needs to work on the lighting circuits, they will be able to trace back to the original panelboard circuit using the phasing. Deviating from the panelboard phasing (like forcing everything to Black/Red) adds unnecessary complexity and can create confusion.3.

Professionalism

Maintaining consistent phasing is a sign of good workmanship and attention to detail. It reflects a commitment to safe and reliable electrical installations.4.

Terminal Block Functionality

You've stated that the feed will be through a terminal block which implies the contactor is not altering the electrical properties other than opening and closing the circuit. With that being said, there is no need to alter the original phases of the conductors.

Specifically Addressing Your Questions



"If my circuit 1 is blue/black, should the lighting circuit that it feeds also be phased blue/black?" Yes, ideally. Maintain the Blue/Black phasing all the way through. "Or can all the circuits be defaulted to black/red since it's technically fed by the contactor now?" You technically could do this, but it's strongly discouraged. It unnecessarily complicates the system, eliminates the link back to the original panelboard circuit identification, and increases the risk of future errors.

How to Implement Consistent Phasing1. Careful Wiring

Ensure that the wires coming into the contactor (from the panelboard) are connected to the terminal blocks and the wires going out to the lights in a phase-consistent manner. Blue goes to Blue, Black goes to Black, Red goes to Red.2.

Labeling

Label all wires and terminal blocks clearly. Use wire markers to indicate the phase (e.g., "L1-Blue," "L2-Black," "L3-Red").3.

Documentation

Document the wiring configuration, including the phase designations, in your electrical drawings or panel schedules.

In summary, while technically you might be able to default to a single phasing scheme after* the contactor, the best and safest practice is to maintain the original phasing of the panelboard circuits through the contactor and out to the lighting fixtures. Flag for review