NeoVim recently added support for True Color mode in terminals that support it. I've tried both Terminal 2.5.3 (343.7) and iTerm 2.1.1, and neither one can display more than 256 colors by default.
This is a script used for testing terminal color capability. When I run it, the 3-byte color mode section at the bottom is just black and green, indicating that support is absent.
Is there a way to enable True Color mode in any OS X Terminal application?