Sudo-aware shell prompt

LOGNAME=$(logname)
UUSER=$([ "${LOGNAME}" = "${USER}" ] && echo ${USER} || echo '$(tput setaf 1)${LOGNAME}$(tput sgr0) as ${USER}')
PS1="[${UUSER}@\h \W]\\$ "

Find a section of your global bashrc, responsible for setting the prompt and modify the PS1 part, replacing \u with ${UUSER}.

Next time you sudo - it will tell you that you are impersonating.