Hashirama knew 8 gates?

[Uchiha Samater]

The point is that opening the 8 gates is something competely extraordinary, it's not something that you can easily see and thus one can not get easily information about how it is to open the 8th gate unless he has personnal experience. In fact I would say that when Madara fought against Hashirama at VotE, not even him could use it because it doesn't the key element you need to use it is an increadibly powerful body. Also, the hypothesis that madara knew only of the colour as a logically expected side effect from opening the 8th gate I think it's a bit far-fetched.

I differ

Well only on that it is difficult to get intel on it ,

I agree that it takes extraordinary effort

I reckon that the technique is exclusive to the Shinobi of Konoha developed by some unnamed so and so , and Madara coming from a time of war more than likely would hear of or see for himself an individual who was able to use it

The information must have been ready available but forbidden due to the damage

how did Gai learn? Who taught him?

Minato stated that he was shocked that Gai was able to learn it

Since it revolves pushing your body to extreme limits I believe the method in gaining it was easy to find out , doing it + the paralysing and fatal drawbacks is a different story , it was left alone by many

Madara knowing or assuming the full gates power based on what we assume as his knowledge and what he has seen from Gai

 

[Byron123]

I differ

Well only on that it is difficult to get intel on it ,

I agree that it takes extraordinary effort

I reckon that the technique is exclusive to the Shinobi of Konoha developed by some unnamed so and so , and Madara coming from a time of war more than likely would hear of or see for himself an individual who was able to use it

The information must have been ready available but forbidden due to the damage

how did Gai learn? Who taught him?

Minato stated that he was shocked that Gai was able to learn it

Since it revolves pushing your body to extreme limits I believe the method in gaining it was easy to find out , doing it + the paralysing and fatal drawbacks is a different story , it was left alone by many

Madara knowing or assuming the full gates power based on what we assume as his knowledge and what he has seen from Gai

You may be right.