Is it appropriate to confront a higher rank when they are blatantly disregarding regs?

Yes and no provided the circumstances. No matter your rank as a service member you are held to the same standards you enforce and are expected to comform to them at the highest level. If you are confident and know the person you sort of have an expectation to do so, but make sure you're fully aware and sure of the violation. Also if you do address it, address it with high respect to rank with no implication that you are trying to get arise or reaction from them. This was discussed in our unit not long ago. Do as you see necessary, but with honor, respect, and the best interest. If someone appreciates your approach then they possess wisdom. If someone retaliates with anger and uses rank to over power you because of your act, then that is a person of great ignorance who repells the urge and hopes of obtaining great wisdom to become the best leader.

Yes, it is appropriate. You just need to do it in a respectful manner. I've been corrected a few times in my career, and I would rather have someone junior to me correct me before I run into someone who outranks me looking like a clown. It's called looking out for each other, and you shouldn't be crapped on for doing it.

With everything in life your best to use allot of tact. Ask the person in private behind closed doors if possible. I would mention that other service members brought it to your attention. That is why you are asking in private not wanting to front the soldier off. If this person has been doing this for along time like 6 months. Then I would say that Command is fully aware of it and they find it acceptable. You could say something like this. " I like your lipstick color, but there were some Airmen that noticed it to and they felt that it's out of regulation. " I dont know all the regs can you help me to understand them better."

Remember the art of tact defines as the ability to tell someone to kiss your ass and have them thank you when your done.
In this case seems like it would have near been impossible.

Do it respectfully.....But firmly and with confidence. Make sure you are right first, then proceed.

Get their attention and ask if you can ask a question in private. It avoids public embarrassment and use a buddy system if person is of opposite sex. Most will be respectful and will give you the time and make life easier.

Yes, but as with what everyone else has stated with tact.

Pics very good and she appeared to be of a racial group that easily plays the “race card” for anything they To get away with.
You could do it privately., which is the right way. Or anonymously by doing a
“What’s wrong with this pic?” and make sure her rank is seen. The base paper would put a bar where her eyes are ..

Yes you should say something, but only use the chain of command to do so. Write a formal complaint and send it up the chain of command.

If you know how to be tactful, you have every right. In case you're like I was a few years ago, I had no idea what tact was and then a MSG enlightened me: Tact is the ability to tell someone to go to Hell and make them look forward to the trip. Be Kind!