This was originally brought up at [[https://en.wikipedia.org/wiki/Wikipedia:Village_pump_%28proposals%29#Darker_section_titles_in_page_history | en.WP VP proposals#Darker section titles in page history]]. A subsequent commenter noted that the text was [[http://snook.ca/technical/colour_contrast/colour.html#fg=808080,bg=FFFFFF | not even AA compliant against the background]] (except with 18pt font).
We think we've found an acceptable AAA-compliant color with [[http://snook.ca/technical/colour_contrast/colour.html#fg=585858,bg=FFFFFF | #585858]].
One of the issues with increasing the autocomment's contrast to the background is with the following .comment text, which is the edit summary-proper. We've been exploring ways of increasing the contrast between these two texts also:
* Change .autocomment to straight letters
* Change .comment to straight letters, setting CSS for .autocomment to italics
* Change .autocomment to use font-weight: lighter (seem to work against desire to increase contrast).
There may be other styles to explore. My recommendation would be the lightest-gray that achieves AAA compliance, and #585858 just happens to be the color we settled on (and not necessarily the best).