When printed on colour paper, your proof pics will have what varies from a slight colour cast to a strong colour tone ranging from sepia-like brown to blue, depending on the settings on the printing machine. Some labs will make adjustments if they are expecting T400 CN, but a lot don't. If they are just for proof prints, with other copies and enlargements to be ordered, I;d say go ahead with the colour printing. It is probably cheaper to just let it runt hrough the machine. If the prints will be the final product, I'd suggest that you go with the B&W paper.(posted 9510 days ago)When TN400 CN first came out, I remember reading about its incredible latitude. One magazine claimed that they exposed from ASA 50 to 800 on the same roll with little or no detectable difference in the final prints. Personally, I've shot it with great results. I use it with old cameras where I'm not too concerned about shutter accuracy, but to determin optical quality and whether or not they actually work. To evaluate shutter speed consistency, I'll shoot chromes. But I digress.
Go for it. Some might be concerned about archival stability of dye-based B&W film, but I think the convenience factor far outweighs it.
Good luck and keep us posted on the results.