Yes, the HTML5 high contrast supports up to 3 different algorithms for most of the browsers compatible with the new HTML5 standards.
The High Contrast feature based on HTML5 makes it possible to have a high contrast rendering working on every Joomla! template without the need to customize CSS classes, this is done calculating the colors inversion automatically so that the high contrast is applied to every Joomla! template with zero customizations.
The high contrast rendering is calculated by default for the standard mode, and can be ruled using the color variation and brightness for the alternative high contrast types.
On Internet Explorer the result of the high contrast will be different because Microsoft still lacks support for HTML5 and the Screen Reader uses a different emulating algorithm.