Now some fonts contain colored emoji, like Adobe Source Code Pro. This is the feature of SVG in OpenType http://www.w3.org/2013/10/SVG_in_OpenType/ Now all major operating system start to support colored font: Windows 10, Android 5.x, iOS, OS X. Most of them use SVG in OpenType enplementation. I hope KDE can implement it, too. Maybe it is the feature of Qt5 and GTK+? Reproducible: Always
After look up some Qt mail list archives, Colored OpenType hasn't been supported by Qt yet. This might not the problem of KDE apps.