Pigment (or really anything that absorbs/blocks light) is subtractive color. CMY(K) is commonly used in printing, but you could just as easily use RGB pigments instead.

There’s a reason CMYK is used for printing. How are you going to mix RGB pigments to get yellow? R+G won’t work. That’s because red ink filters out green and blue light, and green ink filters out red and blue light. So mixing the two you get something that filters out a bit of everything but especially blue, ie. brown. CMY are used for subtractive color mixing because each one filters out just one of the colors we see (C filters out R, M filters out G, Y filters out B) so you can mix them to get most of the gamut you need.

Gender exclusive groups are OK when there is a legitimate reason.

What is a legitimate reason though? Consider…

1. men do not face the problem of being put in uncomfortable situations by women almost anywhere they go, so they have less topics or activities where they feel like they need a men’s only group. For most topics/activities men can go to a mixed-gender group and have the same experience as they would in a male-only group. Women can’t.

You seem to be saying that a legitimate reason would be a need to escape from people hitting on you or the equivalent. How about if you just want to hang out with people of your own gender? Is that not OK? Men do not have the “same experience” in mixed gender groups. Socializing in a single gender group is different from in a mixed gender group and both are important. You are dismissing the need for men to socialize among themselves on the basis that they might make an important decision that should have included people outside that group. Now I understand that this has historically been (and in some cases continues to be) an issue with work-based men’s-only clubs/outings etc, and it should be addressed in that context. But it’s not a valid reason to reject the existence of male only groups or spaces in their entirety, is it?

Case in point: I sing in a male voice choir. I enjoy it not just on a musical level, but also for the fact that it is a male space. It’s not about hating women, or having prejudices about women. It’s not actually about women at all, which is kind of my point. I have enough women in my life, what I need is to be around men sometimes. Nor is it about “we want to address a typical male problem” either, unless you consider difficulty with socializing to be a typical male problem, which, yeah, arguably it is in some cases. But guys just like doing things with guys sometimes. It’s a different dynamic and it’s good for us.

You let them leave the house and meet up with friends, next thing you know they are riding around on bikes! Where will it end?