Sounds like the lab 'corrected' your shots, thus why you are seeing no real blacks. Most labs will probably do the same, and you will either need to find a lab that understands you're shooting night scenes, or else you may need to shoot transparencies to sidestep the issue.
If shooting film, you'll need to use colour correction filters if you want to correct for the casts you're seeing. The advice others have given re: matching your flash to the nighttime illumination present is spot on - filter both your flash and your film to the light source in the scene. As mentioned also, this is going to eat up stops in terms of filtration on your lens, so you're more than likely looking at needing a tripod if you opt to use colour film. If you want to shoot handheld, you're looking at either b&w film, or digital, and a fast lens.
Re: film or digital, both are perfectly useable, you just need to deal with the limitations the night imposes in terms of lower light levels, much higher contrast, and probably mixed lighting sources. However you go, enjoy your shooting, there is something truly magical about the night when it comes to photography 🙂
EDIT: forgot to add, with the advances in high iso in digital, it is possible to shoot in ways handheld in the lowest of light levels that was just simply not possible before. This may be one distinct reason to shoot digitally at night. Being able to shoot relatively cleanly at iso 6400/ 12800 or even more, has opened up new realms of possibility, imo, and although not essential to shooting at night, is one very strong reason to look at shooting digitally.