First of all:
Thank you. I genuniely appreciate this.
That said, I might as well continue this:
Light = additive mixing, paint/printer = subtractive mixing. So CMY applies better to both, at least in theory. There are reasons for RYB's existence, including the fact that perfect cyan/magenta paints are hard to come by, but in terms of pure color theory, CMY > RYB because it covers more colors. RYB's gamut is fairly small in comparison.
AFAIK, the RYB model is generally useful in color mixing, because pure cyan/magenta paints are hard to come by and unpure ones do not exactly conform to color theory. But then they don't exactly conform to RYB, either.
If there isn't a standard at all, the proper answer is "whatever you want". Which is, of course, incorrect, so there IS a standard.
If you're talking about modern standards, CMY is it. (Or RGB for light, but let's ignore this for now) Color science supports it. Even Wikipedia calls RYB "historical".
What I mean when I say
is that it's merely a choice, a theoretical model. That doesn't mean some choices/models aren't better than others.
There is also the practical advantage that CMY gets complementary colors better, closer to the way we actually see. For example, on a RYB color wheel, red and green are complementary (opposite) colors, but that doesn't reflect how we see. You can try a simple experiment yourself: find something intensely red (preferably on a computer, to make sure it's actually red), stare at it for about 30 seconds without blinking, then look at something else. You should see an afterimage and that afterimage will be of a complementary color. And in case of red, it will not be green, but cyan. This is from the RGB/light model (cones in our eyes and all that) but it just so happens that the CMY model works exactly the same way.
The "red/green, blue/yellow" opposites notion does have an underlying basis in the fact that there's no such thing as "reddish green" or "blueish yellow", the brain simply refuses to see something like that. The explanation for that is, however, more complex and totally different. They are opposites in this sense, yes, but they still aren't complementary colors, which is what the RYB model attempts to pigeonhole them as.
In America, maybe. I don't live in America, so I wouldn't know. Then again, my art class didn't teach much about color theory at all. I have encountered RYB only once, in a painting book. So even though I know about it, it's not an intuitive choice for me at all.
You've never tinkered with MS Paint's options as a kid, right?
I'm very tired at the moment and a terrible judge of my tone, actually. I sincerely hope I'm remaining reasonably civil while arguing.