Interaction of border-color and the inset and outset border styles

I just noticed an interesting issue in rendering inset and outset
borders of a given color. There are three basic ways of doing this:

1) Lighten the top and left borders from the specified color
2) Darken the bottom and right borders from the specified color
3) Both

As far as I can tell Mozilla does #3 (as does Opera 6.04, though the
latter changes the color a lot less) while IE6/Windows does #2.  As a
result, using the same border-color for an outset border on a dark
background will make it either nearly-invisible in IE or near-white in
Mozilla or Opera.

Is this something that should remain completely
implementation-dependent?  Or would it be worth standardizing this
behavior somehow?

Boris
-- 
Ninety-Ninety Rule of Project Schedules:

The first ninety percent of the task takes ninety
percent of the time, and the last ten percent takes the
other ninety percent.