Here is the repro: https://jsfiddle.net/29rqecjy/ Any other outline-style on the color input works as expected. When the color input is focused (in that link, it will focus after 5 seconds) outline-style: auto does render. I can see in the inspector that there is isn't a cascade problem.
<rdar://problem/101775128>
I am able to reproduce this bug in Safari 16.5 (STP170) and it does not show 'outline' for color input.
Pull request: https://github.com/WebKit/WebKit/pull/21953