Popular culture depicts ninjas in all-black attire, even in Japan. As the ninjas or ‘shinobi’ were mercenaries trained in espionage, infiltration, ambush, and other covert work, their work was shrouded in mystery. Ninjas are credited with extraordinary powers such as the ability to walk on water and invisibility.
Ninjas frequently wore disguises to appear as monks, beggars, fortune tellers, and musicians. Their clothing did not attract attention and was similar to those worn by samurai or working farmers, which included trousers, a jacket, and gaiters, with lightweight, easily concealed armor.
In addition to their everyday clothing, ninjas likely wore face and head covers to protect their identity for their work. They also tucked in all loose clothing to allow ease of movement and wore lightweight shoes that helped them move soundlessly.
Did Ninjas Wear Black?
The popular perception that ninjas wear black comes from the depictions of ninjas in art, stage plays and performances, and modern media.
Ninjas might have worn black for work that was carried out at night. In everyday life, ninjas likely wore disguises that allowed them to blend in with the people around them, like the farmer’s blue working clothes or costumes of individuals who could move around easily without arousing suspicion.
The idea that ninjas wore black, hooded costumes are in all likelihood a fictionalized or exaggerated characteristic.  In Japan, representations of ninjas dressed them in all black to suggest invisibility, which was a popular artistic trope.
Popular culture likely took the idea from bunraku puppeteers who wear all black on stage. The puppeteers are dressed in black to present the illusion of the puppets moving independently.
Costumes of ninja characters on stage would be all black to depict the ninjas’ skills at moving silently and invisibly when performing their work as covert agents.
While it is possible that ninjas wore black at night or in the battle to hide as they infiltrated enemy camps, it is more likely that ninjas were dressed in hardy working clothes worn by farmers. These indigo-dyed clothes were dark enough to be worn for secret operations. Additionally, the ammonia in the dye was believed to repel mosquitos and poisonous snakes like vipers. 
Apart from these clothes, ninjas wore an array of disguises. They frequently pretended to be firewood gatherers, musicians or other entertainers, fortune-tellers, monks and ascetics, and other people who could move around easily. Monks and beggars were popular disguises as monks were expected and allowed to move across national boundaries while beggars were ignored.
These disguises were used so ninjas could gather information or infiltrate enemy camps for information gathering or planting weapons for attacks.
Did Ninjas Wear Masks?
While ninjas were primarily dressed in disguises to carry out their work, they likely had work that involved sneaking into the enemy camp.
For instances where ninjas needed to protect their identity, they likely wore face covers like masks along with headcovers. It is very likely that ninjas used ‘tenugui,’ a Japanese multi-purpose towel that could be worn as a headcover and face cover.
The word ‘tenugui’ literally translates to ‘hand-wiper.’ This piece of cloth became popular for its convenience and versatility. It was used to clean the home and could be worn as belts, headgear, wallets, and wrapping.
The cloth also became a favorite of martial arts practitioners, particularly those who practiced kendo, as the tenugui could be used to absorb sweat under all the traditional kendo headgear. The ninjas likely wore the tenugui for similar purposes on their heads – to absorb sweat that might impede their vision and cause them to falter if they needed to run or fight.
Apart from using the tenugui as headgear, it was used extensively by the underworld, including thieves who would wear it as a mask by wrapping it around their face. As the ninjas were mercenaries, they were aware of this use of the tenugui and used it to the same effect.
Did Ninjas Carry Weapons?
Ninjas were employed as mercenaries, ranging from surveillance to bodyguarding and fighting. They wore armor and a range of weapons to perform their work.
Ninjas carried weapons, the primary one being the katana. Like all other tools used by the ninjas, the katana would be used for regular battles and footholds and probing devices. Ninjas also used the straight sword ninjato, darts, short swords and daggers, and the star-shaped shuriken.
Ninjas emerged due to civil unrest and were used extensively by the samurai to carry out work that the samurai could not perform on their own. The ninjas started with the same weapon as the samurai, which is the katana. However, the ninjas had a more unusual range of work, so they carried a wider range of weapons.
From the early 20th century, the ninjas began using the straight sword ninjato, which was based on the chokuto and wakizashi, swords used by samurai.
Darts, daggers, spikes, and the star-shaped discs called shuriken were essential elements of ninja weapons because they are long-range weapons that could be thrown easily. Ninjas also used bows and arrows, which were smaller than the traditional longbow in use at the time.
Apart from these, the ninjas used explosives, poisoned darts, firearms, landmines, and acid, all of which they could carry easily and use for their work and facilitate an escape if necessary.
Another weapon that ninjas carried was the kusarigama, a traditional Japanese weapon with a sickle on one end and a spiked weight on the other. The weight was attached to a chair and could be thrown at opponents that were further away. The sickle, called kama, could cut down enemies at close range.
Apart from their range of weaponry, the ninjas also wore lightweight armor that could be easily hidden under their clothes. This armor was similar to chainmail. Called kusari, the chain armor could be worn easily under the jacket or travel cape worn by the ninjas.
Ninjas typically dressed in disguises or regular working clothes like farmers or samurai so they could perform their work without attracting attention.