I'm not a compost expert...I probably only know a teeny, tiny bit of the full science behind composting....However, I DO compost successfully, and have done so for years. We have a homemade two-sided compost bin made from wooden pallets and some door hinges with plywood on the top as an easy cover. We added some swing closures to keep the possums and raccoons out at night, but they don't seem to bother it much anyway.
I also compost indoors in a 5 gallon bucket over the winter (mostly because I'm a sissy and my feet get cold walking to the back of the property with a sloppy bucket of scraps). I add a big pile of earthworms to my winter bucket to help it along. I strongly recommend that practice. It's not the same 'hot' composting I do in my big bin...it's really the little wormies eating and pooping out amazingly perfect composted foodstuffs. Using worms is called 'vermicomposting' and there's a lot of reading available online. You can even buy special worms for your compost. I've never done that. Maybe certain worm types eat more or poop more--I'm not sure. I just grab a bowl-full from the garden before the ground freezes. They are happy in their bucket for the winter. The best part....they are ravenous and eat right through the standard amount of waste we generate. There is NO bad smell, so don't even worry about that.
So back to your greens and browns. You ask how greens go from being high in nitrogen to high in carbon just by drying. I found some 'professional information' that I added below, including a link if you want to read the article entirely, but I'd suggest you just re-frame your thought about the process. Instead of 'going from being high in nitrogen to high in carbon' it's easier to think that as greens dry, they are going from 'more nitrogen' to 'less nitrogen'. As the greens decompose and dry, they lose nitrogen content. The natural outdoor composting methods that encourage quick decomposition produce heat and therefore also 'raise' carbon. There is no flame, but if you'd ever stuck your hand into a steaming pile of compost 'just to see what that feels like', you know that it gets pretty darned warm. True browns, like twigs, teabags, paper shreds, cardboard chips, wood ash, etc.....just simply start off with higher carbon and lower nitrogen.
Compost can be made a very easy process for someone like me that just is after a 'natural' decomposition process---or it can be made much more complex for the person who wants to be absolutely certain their pile has the correct balance. There are meters, and additives, and charting that can be used to have the perfect pile of compost.
I feel that it's a learned art. I've had 'failed batches' of compost....ones that soured and smelled horrendous or ones that wouldn't heat up, for instance. The great thing is that you can learn from the experience and try it differently the next time. We learned quickly that having the bin in the sun was a mistake. It dried out far too quickly for us to keep after. We moved it under a shady tree and had great results. I found that having certain things in the compost actually 'stopped' my previously healthy pile from progressing. (I would NOT recommend putting very, very large pieces in your compost bin....we have a pineapple top and a quarter head of cabbage that have been re-surfacing for about 8 months.) We basically turn it when it looks like it needs it, add water it when it's dry (or leave the lid open when it's set to rain), and occasionally pick up a handful and squeeze it to see if it 'feels right'. And, for the select non-easily-grossed-out-group, (92.6%of the people that love this site would be my estimate), you can always pee in your compost if you feel it's in need of a nitrogen boost. If it smells bad or like pee, stop it. That's enough. I know it's fun, but really, stop.
You mentioned moisture content and questioned if it was a factor in determining if something was 'green' or 'brown'. I believe the green or brown reference is meant to be a loose guide to help composting folks determine what to drop in the pile and when. It really is a nitrogen/carbon ratio thing, though. If you are so inclined, there are a ton of great books available about the 'proper' way to compost. Of course, this site is an invaluable resource for everything you could ever want to know about composting and gardening and a million other things....
We enjoy composting as a low-stress continual experiment. I don't know what the exact elemental make-up is of our compost, but side-dressing our vegetable plants mid-season encourages more blooms and fruit and seems to make the plants happy. I've used it straight out of the bin for potting up houseplants with good results as well.
Oh...we do occasionally add a shovel-ful of ash from the firepit (we only burn dropped branches from the property behind the house and other yard waste).
I'm sure you have already run across the basics for composting, but one very important thing to remember is that you can not put ANY dairy or meat or anything else animal related in the box. Litter box waste and dog poo DO NOT count as 'manure' and should never be used in your compost (I'm sure there's a really good reason, but I don't know what it is). You can add chicken droppings (or if you have a big loose pile of compost, you can put chickens IN your compost pile and let them help scatter and degrade the compost as they scratch around and simultaneously poop, and eat large insects), horse manure, or other farm animal manure.....BUT you have to be judicious about the volume....and you MUST be sure to allow ample decomposition time so that your manure isn't 'hot' with nitrogen when you want to use it. That will surely burn your plants to a crisp very quickly.
One side note....I have had the luxury (?) of using a variety of manure....camel, tiger, and elephant, to name a few. (Someday I will share the comedic story of how I came to have exotic poo to spare, and the outcome of our garden while trying different poo experiments.) Out of those, camel was the best 'traditional' performing poo, but elephant manure is quick to decompose and lower in nitrogen...it can be used after a few days (not to mention the obvious volume). Tiger poo had an unsavory feline odor, but it did keep the coyotes at the back edge of the property that season. We had an AMAZING garden that year.
Here is the 'professional' info I found:
Compost “happens” either aerobically or
anaerobically when organic materials are mixed
and piled together.
Aerobic composting is the most
efficient form of decomposition and produces finished
compost in the shortest time.
Microbes break down organic compounds to
obtain energy to carry on life processes. Under aerobic
conditions, the “heat” generated in composting
is a by-product of biologic “burning,” or aerobic
oxidation of organic matter to carbon dioxide. If
the proper amounts of food (carbon), water, and
air are provided, aerobic organisms will dominate
the compost pile and decompose the raw organic
materials most efficiently.
In general, green materials
have lower C:N ratios than woody materials or
dead leaves do, and animal wastes are more nitrogen
rich than plant wastes are. The complexity of
the carbon compounds also affects the rate at
which organic wastes are broken down. The ease
with which compounds degrade generally follows
the order carbohydrates > hemicellulose > cellulose
= chitin > lignin. Fruit and vegetable wastes
are easily degraded because they contain mostly
sugars and starches. In contrast, leaves, stems,
nutshells, bark, and tree limbs and branches
decompose more slowly because they contain cellulose,
hemicellulose, and lignin.
This is from the following site: webpage
I hope this long-winded response had a nugget or two to encourage you to build on your composting endeavor. Stick with it and have fun with the process. It's actually really rewarding to take 'trash' and make something so healthy and functional. Happy composting!!