Headcanons

"Sanitized Octarians have been sterilized of life's energies with blended ink created by Commander Tartar. Subjects who are chosen as candidates to aid in this ink's creation are tested beforehand through the Kamabo Co. underground research facilities; if successful, the tests conclude with Tartar tricking the subjects into being blended to help create the ink. The process of sanitizing Octarians with this ink results in them losing all memory and identity, and submitting to Kamabo Co.'s ideas. Marina notes that the sanitized Octarians appear to have no pulse or signs of life."
...
"Their voices sound more digital and compressed, and when splatted, they briefly produce glowing blue pixels and glitch-like squares."
(From the splatoon wiki)

Ok, sanitization is a very tricky thing to talk about given the fact it seems to have so many different effects, so i'll split this up a bit

Partial sanitization

Eight is said to be sanitized, but it only seems to have affected their memories, rather than their appearance, which leads me to the first thing i'd like to define, partial sanitization is a procedure where the subject's memories are extracted and reshaped into mem cakes, this is used as a strategy to get the subject to perform the best in their tests, with them working under the assumption that the promised land is real. this procedure invokes amnesia in the subject, which can be treated with returning the mem cakes belonging to them.
This typically has no permament effects, aside from a foggy memory around the time the subject was partially sanitized.

Complete sanitization

This is the main kind of sanitization, which carries the side effects of turning the subject green, Discolouring their tentacles and permanently altering their ink. The procedure aims to instill an unwaivering loyalty to Kamabo Co. in the subject, to remove any external doubts and feelings that may interfere with their work for the company, Cori underwent this procedure after failing the testing track due to the proficient marksmanship she showed, however, her procedure was mishandled, which lead to her glowing pupils
Many effects of this are permanent.

"The sanitized Octarians' ink, which is the same as the one used to sanitize them, is cyan with a marbling pattern and resembles dishwasher detergent or hand sanitizer."
(From the splatoon wiki)
It's a blended ink. I think it looks like it has a marbled pattern. If you bathe in that ink for a long time, your head will be repainted with Kamabo Co.’s ideas.
(From a SRL Q&A)

I do think there's gonna be SOME different concentrations of ink, as eight doesn't get turned green IMMEDIATELY after being shot with ink, and is even shown as having residual left on them in promo art [pictured]
Rather, I think that it's generally a lower concentration used by footsoldiers, and the higher concentration stuff is used sparingly in cases like agent 3's mind control... which also makes me believe that sanitization takes some time to complete as tartar had no reason NOT to try and permanently sanitize 3, yet they were controlled for a time...

High concentration ink is also detrimental to ink production, since there is an increased strain being placed on the body, this concentrated ink would probably sting to touch aswell.
additionally, higher concentration ink is used by Cori in my oc lore, experimentation on her lead to her ink being permanently concentrated...
I also think that sanitized ink would be "incompatible" with regular ink applications if this makes sense?
it doesn't mix well, you can't have it change to team colours, stuck with the gradiented hair... Of course this only applies to complete sanitization though

"Mem cakes are compressed memories belonging to Kamabo Co.'s test subjects. They are awarded to test subjects as they pass tests as part of convincing them the "promised land" is real."
(From the splatoon wiki)
"Acht: I'm surprised you recognized me, Marina. I don't look quite how I used to.
Marina: Hm? Well, sure, but... your voice and whole general vibe were a dead giveaway."
(From Sdodr_TalkElevator.msbt)

I think that mem cakes would have a partially spongy texture, though would be able to sustain damage given mistreatment which would be expected in the kind of storage areas Kamabo was housing them in (Kamabo & Storage)
Additionally, dialogue in side order alludes to the fact that Marina was able to recognise Acht despite their sanitization, which means that sanitized subjects are still identifiable *after* their sanitization

"Mem cakes are compressed memories belonging to Kamabo Co.'s test subjects. They are awarded to test subjects as they pass tests as part of convincing them the "promised land" is real."
(From the splatoon wiki)
"Acht: I'm surprised you recognized me, Marina. I don't look quite how I used to.
Marina: Hm? Well, sure, but... your voice and whole general vibe were a dead giveaway."
(From Sdodr_TalkElevator.msbt)
"After collecting the four thangs, the test subject is carefully preserved, as proof that they existed in this world."
(From a SRL Q&A)

There's actual gameplay of where kamabo stores things in oe, during the abandoned station sequence you can find your way through a storage area with many boxes sealed away behind glass, I think that the "proof that they existed in this world" would be the mem cakes from the subject, that are placed into these storage areas by Kamabo after either sanitization or blending

Also, I wouldn't assume kamabo is above storing individuals either, something along the lines of oe's character select sequence [pictured]. Cori was kept in this kind of storage for a while after her failed [link to page when it exists] mission, with her only awakening after the facility lost power. Her mem cakes were destroyed in storage by one of her commanders.

"It appears that Octarians are a part of the army at an early age as revealed by documents on Marina, where she started elementary training at the age of six, and designed weapons when she was ten."
...
"While the Octolings of the Splatlands seem to share their culture with the Inklings there, the Octarians of Inkadia have a very different culture from the Inklings, and are frequently described as diligent, serious-minded and loyal to their leader"
(From the splatoon wiki)

asdasdasdasd mention acht

"Marina was a renowned genius in the Octarian world, and she had the respect of many. They weren't acquaintances, since Agent 8 was a trainee, they just knew of Marina one way or another."
(From a SRL Q&A)
"Acht: Yeah, there's like no chance your stuff isn't in a garbage compactor somewhere."
(From Sdodr_TalkElevator.msbt)

This is the pivotal part in Cori's lore and what lead to her entering kamabo's facilities... There's a similar case where Marina also deserted (see Marina) that kind of mirrors what she went through. I'd assume that deserters are thought of lowly in the army, and people often extend no sympathy after they are discovered after the chaos caused by Marina's departure
Additionally, Cori knew of Marina before her desertion (as did many other octolings) yet believed she had integrated safely unlike those around her, this would've contributed to attempting desertion herself
also, marina left with a travel bag [pictured], while cori only left with a satchel bag, which is a nice comparison

"Octarians are stated to have a language different from Inklings. In the Japanese versions of the Splatoon games, DJ Octavio speaks only in katakana, which is usually used to display foreignness in the way a person speaks in Japanese culture ... As seen with the dialogue from scanned Octoling and Octoling Octopus amiibo, defected Octolings often have difficulties speaking the language of Inklings and make several grammatical mistakes."
(From the splatoon wiki)

This is something Cori also struggles with, having only been able to connect with Lumine because their shared knowledge of the octarian language.
I'd imagine it's obvious splatlandian wasn't her first language, but she can speak it a decent amount.
While i'm on the topic also, I'd imagine deepsea is it's own language as it has a script, this is what Cori would be most familiar with post-sanitization.