Look at your home directory and the file .bashrc. Find these lines:
# uncomment for a colored prompt, if the terminal has the capability; turned # off by default to not distract the user: the focus in a terminal window # should be on the output of commands, not on the prompt #force_color_prompt=yes
Uncomment force_color_prompt=yes, save and login again.
For root to have colored prompt, but with different color f.e. red, find the same file in .root directory and also uncomment force_color_prompt and look for:
if [ "$color_prompt" = yes ]; then PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ ' else PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w\$ ' fi
Look for number 32, marked with green color and change it to 31 (red), save and re-login.