24-bit color support (\033[38;2;rrr;ggg;bbbm) has been mainline in both Konsole and in libvte-based terminal emulators for many years. 16777216 colors. That's still not every color, but it's every color your monitor can display. When I wrote http://canonical.org/~kragen/sw/dev3/gradient.c in 02016 I had it in Konsole but not libvte, though I think it had been added to libvte upstream. http://canonical.org/~kragen/sw/dev3/gradient.png

Color in terminal emulators was one of the main perks of Linux over other Unixes for me at first!