Two-spirit as well as the other terms in the Culture-exclusive Genders folder are genders that are specific to certain cultures and should not be used by people not of that culture. If you're not sure you're able to use this, feel free to send an ask on ask-pride-color-scheme.tumblr.com, I have followers that could help you out!
From the submission [Link]:
"[Two-spirit] is an exclusive gender for Native Americans. In essence, a person has the spirit of both woman and man within them (hence the name!), so it could be thought of as a cultural version of bigender. This term is also used by trans Native Americans even if they wouldn’t describe themselves as bigender specifically, just trans or nonbinary in general. In a way it’s actually sort of an umbrella term, as most tribes have a tribe-specific name for Two-Spirit. For example, I’m Lakota, and in my tribe we call it winkte!
[...] Basically, the two feathers represent woman and man, and the circle represents unity in one. It’s most commonly seen with the gay pride flag, though personally I think I’d prefer it with the trans or nonbinary flag background. [...] Two-Spirit is meant to be a gender identity, and I feel like having the gay pride flag might get people confused and think it’s a sexuality. That’s just me though!
Also! I know this video shows yet another Two-Spirit flag made by Ma-Nee Chacaby (she is also Two-Spirit, a major activist in the Native American LGBT+ community, and she has her own autobiography here!)
Lastly, I want to finish this off with a few websites for further reading on Two-Spirit, besides what you might find on Wikipedia: here, here, and here. Please note that there may be some discussions of slurs in these links, so take care. Thank you very much for reading!"