You can get a black and white image with Tubed Nightvision, if it is white phosphor tube. Although it does have a slight blue or grey tone, but I suppose that depends on your colour vision standard...one persons blue tint is anothers grey tint.
Mr B has basically described the differences between tubed and digital NV better than I could have.
I will add though, if you didn't know already, that any tubed night vision is strictly night use only unless it is very special with special filters and i.e. very very expensive. You cannot expose a turned on tube to any form of daylight or artificial light other than IR, even powerful IR's can eventually downgrade the tube. The upside is that you can use it with without an external IR if needed, although this effect is best had with gen 3 or it's better or equivalent in a Photinos tube... XD4 XR5 etc.
Digital night vision can be used in the day without damaging the internals and it is always going to be cheaper than Generation 3 plus and in most cases even gen 2 plus. Some digital units can also be used well apparently with no IR, mainly in the dusk/twilight to night transition like with the Ward digiceptor scope....of course its all weather and conditions dependent with any night vision!
You could argue that these days with the images improving and digital being cheaper, it's a no brainer...however I think even at the moment, a state of the art tube has the upper hand over digital in terms of image sharpness and definition, you just need to look after it and use it properly.
Sorry for the essay! I have been trying out alot of units the past 3-4 years. I have settled with a cheap photon digital unit on a .22lr as its perfect for one of those and can use in the day also...not to say its not good for centrefire because it is, very good units. However I think a tubed add-on to a day scope has that edge, particularly for your longer range stuff...whether it be archer or pvs14 or similar.
I hope that helps you somewhat
