For me it is DEFINATELY the colour/color RED.
When I used to drink alcohol as a way of coping with life it didn't bother me too much, but after I stayed at a treatment centre & returned home, upon walking into my sitting room I was literally bombarded by all the colours.
On the bookshelf there were so many different coloured books, and the red ones just sent me into overload. It was visual sensory overload.
As a result I got rid of ALL my books apart from 5 favourites (3 of which have red on them but as it is such a small area it is OK).
To me, things that are Red stand out from everything else. Maybe that is the same for everyone as RED signals DANGER & Red is the colour of blood.
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We, the people on the Autistic Spectrum have a choice.
We can either try to "fit in" with the rest of society, or we can be so egocentric that we can't be bothered.
I choose the actor. I observe NT's. I listen to their socializing. I practice it, so in social situations I can just emulate/mimic what is expected.
It isn't natural for me, but it enables me to "fit in".
It is VERY tiring and draining, but at least we can appear like them even though it is an act. Like being on the stage.
They can't see it is emulation, and so we are accepted.