Thanks for being curious! I've contacted the author and this information will help indeed to make the script backward compatible.

I couldn't help myself, I was curious, and the relevant change is the one that added support for octal escape sequences in double-quoted strings in version 3.8.0.

In old versions of Octave,

>> "\033" == char ([0, 0x31, 0x31])
ans =

   1   1   1

this double-quoted string contains three characters, a NUL byte, and two 3s.

In recent versions of Octave (starting with 3.8.0), this is parsed as an octal escape sequence. The cprintf.m script you pointed to makes use of this to build its terminal escape sequence strings.

In an Xterm(271) (under Ubuntu 12.04) this script:

https://sourceforge.net/projects/cprintf-m/

generates calls to printf, like printf("\033[1;31mtest\n"), but it does not print colored strings (something like cprintf("red","%s\n","test"), will leave the system terminal idle. It works fine in a Xterm(297) on a different system (Ubuntu 14.04). Both terminals were in the default Ubuntu configuration (i.e. '*customization: -color' option included).
According to the current octave documentation, that should work; the release notes for 3.8, 3.6, 3.4 do not mention escape or printf in this regard.