multibuild_foreach_variant in multibuild.eclass uses tee which leads to colours not being shown for e.g. Meson. This can be seen with any multilib ebuild, like systemd-utils-255.13 (ebuild ... clean configure). All of Meson' configure tests are in black/white rather than green/red.
I'm not really sure if this is a Meson bug or not with how it detects a TTY / doesn't allow you to always truly force colour (MYMESONARGS="Db_colorout=always" doesn't seem to cut it).
(In reply to Sam James from comment #1) > I'm not really sure if this is a Meson bug or not with how it detects a TTY > / doesn't allow you to always truly force colour > (MYMESONARGS="Db_colorout=always" doesn't seem to cut it). -Db_colorout is an option that controls how meson performs compiler setups, for compiler options that are agnostic across all compilers (i.e. there is no -Dc_colorout versus -Dcpp_colorout versus -Dfortran_colorout). Meson provides no knob to control colored output of the `meson` program itself, just a TTY check (literally, it does os.isatty(sys.stdout.fileno()) and emits colored output if isatty says it is a TTY).
