Please don't. Strong contrast helps readability; grey-on-color is lower contrast than white-on-color.
Most HN threads linking to a site that has light-grey-on-dark-grey or dark-grey-on-light-grey text have at least one (off-topic) complaint about site style. Let's not make HN one of those sites.
Most HN threads linking to a site that has light-grey-on-dark-grey or dark-grey-on-light-grey text have at least one (off-topic) complaint about site style. Let's not make HN one of those sites.