When HTC announced the HTC One (M8) earlier this week, the only colors available initially were Gunmetal Gray, Amber Gold and Glacial Silver. There are many buyers of smartphones who look for devices with a little more pop and want other colors. HTC seems to be preparing to respond to these demands with at least two new colors – Stealth Red and Stealth Black. These colors were discovered after users performed some searches on Google and discovered ads for these variants showing up at the top of the search results.
Given the results are ads implying HTC is paying for them, even though they may be part of a larger package, this is probably a good indication that the additional colors are not far off from being released.
source: HTC Source