That printf command is, strictly, wrong. It was pointed out some years ago, when people started adopting this, that ITU T.416 has a colour space parameter before the RGB values.
A few terminal emulators nowadays get this right and accept the full 9-parameter form, with colons.
JdeBP|10 months ago
A few terminal emulators nowadays get this right and accept the full 9-parameter form, with colons.