I have tested the below code in msys2-emas26 of window7, seem that internal-border
can not be overrrided.
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(defface test
'((t (:inherit default :background "green")))
"Face used by the ivy-posframe."
:group 'ivy-posframe)
(setq face-remapping-alist '((internal-border . test)))
(make-frame '((internal-border-width . 100)))
(redraw-display)
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