Origin of the Bulgarian flag

[Liberator of Makedonija]

This YouTube video summarises all the different theories surrounding the origins of the flag:

https://www.youtube.com/watch?v=aVVGWGTnbiU&t=603s

[Soldier of Macedon]

According to Wikipedia, this was the flag utilised by the Bulgarian legions in Belgrade in the 1860's

There is no history or elaboration mentioned on that page in relation to this flag. There is no contemporary photo of it either. There is another flag on the same page which was apparently used by this legion. It has the following description by the person who posted it:

The banner of the first Bulgarian legion from 1862. It was destroyed by the Serbian authorities in 1867. A report is kept in Serbian archives to the Minister of the Interior, which fully describes the type of the banner. The report states that it was a green field with a lion standing on its hind legs with a crown on its head. The lion was standing on the Ottoman flag. On this green flag was written "Freedom or death". Some of the banners of the 1876 April rebellion give an approximate idea of what the flag of the First Bulgarian Legion looked like. I used such a banner as a model for creating this pattern.

I can't verify any of that, but it is obviously in reference to a different flag. I'm not suggesting that the tricolour flag mentioned in the beginning is fake, but I wouldn't put it past those wiki bulgars. Anyway, there is the below flag from the time of the Russo-Turkish War 1877-78, the description states:

Flag made by Stiliana Parashkevova for the Bulgarian volunteers (Opalchentsi) in the Russo-Turkish War (1877–1878). Inscription in Bulgarian: България (In English: Bulgaria). The flag is the basis for the contemporary National flag of Bulgaria.

Looks like a copy of the Russian flag based on the order of colours (except they've replaced blue with green), which would make sense given the amount of Russian influence and involvement in Bulgaria. Not sure what the significance of green is for them, perhaps they got the idea from the Ottomans. There is nothing in the Bulgarian constitution regarding the origins of their flag either. See: https://parliament.bg/bg/21

[Liberator of Makedonija]

Flag of Eastern Rumelia, annexed by Bulgaria in 1885.

[Liberator of Makedonija]

The flag raised by Bulgarian volunteers during the Russo-Turkish war. Interestingly this one incorporates Pan-Slavism and Orthodox Christianity, no presence of the typical green and red.

[Liberator of Makedonija]

According to Wikipedia, this was the flag utilised by the Bulgarian legions in Belgrade in the 1860's

[Liberator of Makedonija]

Honestly, I thought it was simply a copy of the Russian flag, except they added green. Am I right to assume that Russians had major influence when this nation was first formed?

Russia pretty much single-handedly created Bulgaria so yeah you are right. Even if that is the logic behind the flag, what does the green mean?

[Starling]

IIRC the Russian army was largely in Bulgaria and it negotiated Bulgaria's independence in exchange for selling Macedonia back via the San Stefano agreement.

[Dejan]

Honestly, I thought it was simply a copy of the Russian flag, except they added green. Am I right to assume that Russians had major influence when this nation was first formed?

[Liberator of Makedonija]

Flag of modern Tatarstan and flag of modern Bulgaria respectively

[Liberator of Makedonija]

I am aware of the origin and meaning of most of our surrounding neighbours but the Bulgarian flag has always stumped me and I have seen it to be a bit of an outlier in a common trend of Christo-Roman symbology. As a tricolour the colours must have some meaning, I can only assume the white means peace but as to what the green and red mean I do not know. I noticed that green and red in a vertical row design is the same as the flag of Tatarstan, could those colours represent an old Tatar identity?