In case this may be helpful for someone who just needs to show colors rather than output, as a hackish workaround (and FYI), since GitHub supports Unicode (as Unicode, numeric character references or HTML entities), you could try colored Unicode symbols, though it depends on the font rendering them in color (as it happens to be appearing for me on Windows 10 and Mac 10.12.5, at least, though on the Mac at least, the up/down-pointing small red triangles don't show in red):
- RED APPLE (🍎):
- GREEN APPLE (🍏):
- BLUE HEART (💙):
- GREEN HEART (💚):
- YELLOW HEART (💛):
- PURPLE HEART (💜):
- GREEN BOOK (📗):
- BLUE BOOK (📘):
- ORANGE BOOK (📙):
- LARGE RED CIRCLE (🔴):
- LARGE BLUE CIRCLE (🔵):
- LARGE ORANGE DIAMOND (🔶):
- LARGE BLUE DIAMOND (🔷):
- SMALL ORANGE DIAMOND (🔸):
- SMALL BLUE DIAMOND (🔹):
- UP-POINTING RED TRIANGLE (🔺):
- DOWN-POINTING RED TRIANGLE (🔻):
- UP-POINTING SMALL RED TRIANGLE (🔼):
- DOWN-POINTING SMALL RED TRIANGLE (🔽):