The October 2015 update KB 3085579 for Outlook 2013 introduced the option to set the font, font size and font color for the message preview (AutoPreview) in Outlook.
3085579 October 13, 2015, update for Outlook 2013 (KB3085579)
Message preview can be enabled in the View ribbon and can be set to Off, 1 line, 2 lines, or 3 lines:
The message preview dialog allows you to select a font:
Unfortunately, the color options Auto and Black are included in the list, but cannot be used. Even if you select them, Outlook will fall back to Gray (Custom).
This is the expected behavior as having the message preview font set to Black causes some incompatibilities with the Office color theme and does not align with the color scheme used in Outlook 2016. Therefore, this color option isn't recommend.