Ninja like those depicted here are entirely fictional to begin with, the closest equivalent in ancient Japan would be an Shinobi assassin that would most likely have worn a disguise to make them blend in, so the camo costume is about just as plausible as the black theatrical costume Ninja are typically depicted in.
You do make a point, which is why I would prefer a grey or blue costume (it seems more likely). They probably did wear something similar to the traditional costume at times (in different colours), but as you say not always (most would, indeed, wear disguises; it depends on their function), but they seem to have had armour under their clothing if Ninja museums are to be believed. In fact shinobi are not only assassins, but also spies and saboteurs so they would have worn a variety of clothing.
The shinobi in the black might be a tad a-historical, but they have precedent due to their depiction in Japanese theatre and in prints from the time, or just after, that they existed in.
''Shinobi'' is also just an alternative reading of the Chinese character that make up the word ''Ninja/Shinobi''.
As for the Batleth, the two single handed crescent shaped weapons that come with the black costume set (they're listed as Batleths too) look closest to Deer Horn Knives which are traditional Chinese Martial Arts weapons.
I thought they looked like something a Chinese martial artist may have. I am not as knowledgeable on Chinese martial arts, but I am sure they are too big, however. Whatever the case, I think they make the figure look a tad ugly (and inaccurate, as Ninja did not use many Chinese weapons).
They seem to have done a search on the internet and found the ''Black Ronin Ninja Ring'', which, as you say, if entirely fictional but seemingly based on the weapon you mentioned. Though, the batleth I was refering to, actually comes with the camo ninja, and I mismatched the weapons. The weapon with the black ninja does look very ridiculous to me, anyway.
It's the Hollywood version which is what Ignite and Sideshow are selling. Shinobi I sincerely doubt ever wore anything like what we would call a Ninja. I edited my above post to be more specific.
To be fair, sometimes Japanese call ''shinobi-no-mono'' ''ninja'' too, it is just the on'yomi reading of ''忍者'', rather than the kun'yomi (which is more accurate to the native word). Shinobi is more traditional and more common (obviously), but due to the system of kanji, ''ninja'' is not technically incorrect, just far less common.
And they do appear in art from the Edo and Meiji era looking much like the ignite figures:
https://en.wikipedia.org/wiki/File:Hokusai-sketches---hokusai-manga-vol6-crop.jpg
This does not mean that a ninja, or shinobi, did look like that. It could idea be an artistic choice. However, I think it is more likely that they would have worn something like that for sabotage etc. but black is less likely than blue, brown or grey, because black doesn't really blend in as well in the dark, it is a little too dark most of the time. I think the perfect shinobi figure would include a peasant (or even samurai or monk) outfit along with the classic shinobi attire in blue or grey. The Ignite figures in black might not be historically accurate but they are artistically accurate, more or less.
AH! yes, the traditional Shinobi never wore "ninja" garb.
REAL shinobi would wear what any espionage agent would wear. They want to blend into the environment they were infiltrating.
I wouldn't say that they would not wear anything akin to what shinobi wear in prints (I would not call it ''Hollywood'' because the classic ''ninja'' is a Japanese convention from at least Hokusai's day, not an American one).
Other than the colour ''Ninja Outfits'' (shinobi shozoku) are actually pretty generic Japanese clothing, especially for travelers, workers or those in training. Shinobi would wear tighter fitting clothing, something like keikogi that is used today, or at least tuck in their loose clothing so it is worn tighter. They'd also probably have concealed their faces, or at least worn a zukin, which is a hood:
https://upload.wikimedia.org/wikipe...a_travel_cape_and_zunin_with_kusari_armor.jpg
THe garb we think of, that ignite and Hollywood sell has it's origins in Kabuki performance art.
It originated in Bunraku, I believe. Bunraku is a puppet theatre in which man dressed in black robes to disguise themselves whilst controlling puppets. It is similar to Kabuki.
I'd think they look ridiculous even if shinobi did not actually exist at all and were simply a western convention. The fact remains that they wear tattsuke hakama (pants with leggings) and kimono (''shirt''), real Japanese items of clothing that are from history, even if kimono and hakama are often warn today formally, and should ideally never be camo. Practical distractive-pattern camo, which is very modern, would never be worn with clothing that to modern eyes is impractical. Fictional assassin or not, he should still have believable clothing...in my humble opinion.
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