What
The built-in colour themes used to define a colour named autoAcceptShimmer. It has been removed from all of them, and nothing in the interface uses it any more.
Why
The name points to a shimmer effect on the auto-accept mode indicator. In practice, that indicator no longer has a separate shimmer colour to draw with.
Something disagreesSomething we can check disagrees with this entry, or the writer said they could not settle it.
The writer flagged doubt
It is not confirmed what appeared on screen in this colour before it was removed.