Yes. But 'grain' in the context of a (lith) print is maybe a little confusing. Any B&W emulsion is essentially tiny particles of silver halide - these are the 'grains'. After all, they're just tiny morsels, specks tidbits...well, grains! Think of the order of magnitude of 10um or so - pretty darn tiny. Of course, if they're on your film, and you then enlarge the film, the grain becomes visible in the print as the coarse pattern we all know. But now we're talking about print grain, and that's still the same principle...but the effect is different.
In normal print development, we expose the print and then basically develop the heck out of it. Or, put more formally: we develop 'to completion' - i.e. until every little speck (grain) of silver halide that has had some light fall onto it is developed into a nice, little (tiny!) lump of silver. Again, the particle size is in the micrometer order of magnitude - for convenience's sake, let's stick with the 10um from above. Well, turns out that if you put a truckload of these tiny 10um silver particles right next to each other, it doesn't reflect much light anymore. In other words: it's pretty much black. For a normal print, that's what we want - if we put a lot of those grains side by side, it's black. If we allow a little more space between them, we can make shades of grey: just some tiny black specks with paper white in-between.
So what's the deal with 'varying the grain size' as is done in a lith print? It's very simple (in principle...): instead of developing the heck out of our print and allow all those exposed little specks to grow to their maximum 10um size, we develop them way less. We allow them to grow maybe 1um, or 5, or maybe 8. But not 10...expect maybe the ones in the deepest shadows, where we want some real black. What's the significance of this smaller particle size? Well, funny thing, but due to the fascinating laws of physics, tiny silver parts that are smaller than about 10um reflect some (or sometimes, a lot) of light. And not just random light, but specific wavelengths. That's right - they look colorful! The tiniest grains (around 1um as I recall) show up as yellow, if you allow them to grow just a little larger, they become reddish, and if you allow them to grow yet larger, they transition through brown towards black - and if you coax them to grow just a little bigger than they can on their own (i.e. by throwing some gold toner at them), they shift to a cold bluish tone.
Now, keep in mind we're still talking about grains less than 10um in size. Hence, you won't see individual grains with the naked eye, or even with a good magnifying glass. You can see them under a decent microscope, but your lith prints are never going to look grainy 'in the film sense' just because of these micrometer-sized grains. Yes, lith prints do look grainy (sometimes/often), but that's due to grain clumping, i.e. specks of grain 'infecting' others nearby in development (it's a little more complex than that, but the analogy kind of works). So the story about manipulating grain size is all about where the color of a lith print comes from. Coincidentally, it's essentially also (part of) the story about toning.
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