The answer to your actual question (straight from WebKit's default html.css
styles) is this:
:focus {
outline: auto 5px -webkit-focus-ring-color;
}
The value of -webkit-focus-ring-color
is determined on each platform separately (if you're super keen, you can look for WebCore::systemFocusRingColor
). In practice, the values vary by platform.
In Safari v6 and Chrome v20 on OS X Lion, the actual value is:
outline: rgb(94, 158, 215) auto 5px;
…and in Chrome v20 on Windows and Chromium v18 on Linux, the value I got was:
outline: rgb(229, 151, 0) auto 5px;
As described in this great StackOverflow answer, you can run this jsFiddle to calculate the outline colour on your own machine.