In case it helps anyone, have a few random tips on dealing with miscellaneous sensory stuff that I've picked up over the years:

Fragrance-free toiletries are your friend for times when you frankly don't need any more sensory information coming your way, but not all are created equal. If you're in the UK, Sanex Zero% (not sponsored at all lol, and there are almost definitely more brands out there, but this is one I can vouch for) is a range of genuinely colour and scent-free toiletries. There is a very faint soap-like smell if you concentrate, I admit, but that's probably unavoidable, and it's still a drastic improvement from some allegedly scent-free products. It doesn't look like it's readily available outside of the UK, though

If a topic has a certain colour to you, it will both be less distracting in the moment and help your memory later on if you write notes on it in that colour. You can tailor how many colours you use to your own needs. E.g. if changing pens constantly will be more distracting than using the wrong shade of a colour, stick to a basic set. If the opposite applies, and you need the shades to be precise, you might want to invest in a more expansive set, like a case of art fineliners (and I'd recommend practicing the art of switching between pens quickly if you're going to have a lot of colours whilst taking notes in a timed setting such as a live lecture). Or, if you have the option of typing, computers have essentially infinite colour options, and you don't need to worry about popping lids back on whilst trying to pay attention!

Regarding the last point, I know some schools do insist on everything being written in black (which doesn't make any sense to me, but... anyways). In my experience, highlighting over the black text in different colours is usually still allowed in these cases, provided it's your own notes and not an exam or essay or something. But helpful tip- if you're going to try this approach, do not use a gel fineliner for the initial writing! It WILL smear when highlighted!

If looking at a full page of text is overwhelming, you can use a blank sheet of paper to cover up the parts you're not actively reading on paper, or zoom in so you can see less text at a time on a computer

If you chew on objects of any kind, or hold things in your mouth for sensory input, get some silicone 'chewelry'. I used to chew on my collars badly enough that most tops were rendered unwearable pretty quickly, up until I invested in a few chew necklaces in November to see what all the fuss was about. Those things are truly game-changing, IMO. The silicone is odourless and tasteless, you can choose the firmness, textures and colours you want, and there are subtle designs available that look like a regular necklace or wristband if you prefer low-key. I will say that some of my necklaces did have a weird, unpleasant powdery texture to the surface when they arrived, but after multiple washes that has now resolved

(I first heard this one somewhere else, but I've used it with success, so here it is anyway) Telling people that you have a migraine works as an 'excuse' for a lot of sensory things, including needing to leave an overstimulating area or situation, lights, sounds or smells being too intense, needing to wear ear defenders or dark glasses indoors, wanting quiet, darkness and solitude, or not wanting to eat specific foods (as migraines can both be triggered by certain foods and cause nausea). And it's not technically lying either, since if you did Do The Thing and end up going into sensory overload, there's a good chance you really would end up with a migraine if you're prone to them

If people struggle to understand how grapheme-colour synaesthesia or OLP work, point them in the direction of the British kids' shows Alphablocks and Numberjacks (each letter or number in these shows has a set colour, age, gender and personality)

If you tend to panic and/or lose your vision with unexpected loud noises, laying out and learning a pattern of simple steps for yourself to take in case of, for instance, a fire alarm going off, can be the key to not freezing up. I feel like an anecdote will explain what I mean with this technique best, so here goes...

(this anecdote features myself in meltdown mode, so I'm popping it under a cut in case peeps want to avoid that description)

When I lived in university halls, the fire alarm would regularly go off in the middle of the night thanks to intoxicated students attempting to cook. The first time it happened, I was not expecting it at all, but luckily the alarm featured a voice stating 'leave the building' as well as the typical siren, which kept me grounded enough to get outside- tripping over along the way- before having a full meltdown in the car park at 4am (great fun... not). I vowed to never let that happen again, so as preparation for future fire alarm activations, I a) placed a pair of slip-on shoes right next to my bed so I wouldn't have to guess where they were and fumble about with straps without being able to see, b) taught myself a mantra of 'shoes, out (into the corridor), wall (to guide me to the door whilst I couldn't see), door' to prevent my brain from freezing up in the moment (the alarm didn't always have the voice that had helped me, for some reason), and c) had a day of practice where I set multiple phone alarms for random intervals throughout the day, so I got experience of going through the process without prior notice. The future fire alarms after that were still not pleasant, but the ingrained routine always kicked in, and in fact I was always the first person outside