PREFIX/etc/bash/bashrc does not recognize xterm-256color terminal as color capable. this was fixed in main gentoo repo long ago, see e.g. bugs 141771 or 165305. cf. commit comments under https://gitweb.gentoo.org/repo/gentoo.git/log/app-shells/bash/files app-shells/bash/files/bashrc should be synced with main gentoo repo. and while we are at it, files/dot-bash_profile should also be synced with main gentoo repo.
synced, thanks!