Verificando a variável PS1:

echo $PS1

 \033[<bg-color>;<fg-color>m

Sendo <bg-color>:

       40   -> preta
       41   -> vermelha
       42   -> verde
       43   -> marrom
       44   -> azul
       45   -> mangenta
       46   -> ciana
       47   -> cinza

<fg-color>:

       30   -> preta
       31   -> vermelha
       32   -> verde
       33   -> marrom
       34   -> azul
       35   -> magenta
       36   -> ciana
       37   -> cinza

Teste a combinação:

PS1="\033[47;30m[\033[47;31mDebian\033[47;30m] \t\033[0m\n\u@\h:\W\$ "

Outros exemplos:

PS1-usuario:

PS1="\[\033[01;32m\][\u@\h\[\033[01;37m\] \W\[\033[01;32m\]]\$\[\033[00m\] "

PS1="\[\033[01;32m\]┌──[\u@\h\[\033[01;37m\] \w\[\033[01;32m\]]\n└─$\[\033[00m\] "

PS1-root:

PS1="\[\033[01;31m\][\h\[\033[01;36m\] \W\[\033[01;31m\]]\$\[\033[00m\] "

PS1="\[\033[01;31m\]┌──[\u💀\h\[\033[01;36m\] \w\[\033[01;31m\]]\n└─#\[\033[00m\] "

Referência completa sobre os valores possíveis.

   \a     an ASCII bell character (07)
   \d     the  date  in  "Weekday  Month  Date" format
          (e.g., "Tue May 26")
   \e     an ASCII escape character (033)
   \h     the hostname up to the first `.'
   \H     the hostname
   \j     the number of jobs currently managed by  the shell
   \l     the  basename of the shell's terminal device name
   \n     newline
   \r     carriage return
   \s     the name of the shell, the  basename  of  $0
          (the portion following the final slash)
   \t     the current time in 24-hour HH:MM:SS format
   \T     the current time in 12-hour HH:MM:SS format
   \@     the current time in 12-hour am/pm format
   \A     the current time in 24-hour HH:MM format
   \u     the username of the current user
   \v     the version of bash (e.g., 2.00)
   \V     the  release  of  bash, version + patchelvel (e.g., 2.00.0)
   \w     the current working directory
   \W     the basename of the current  working  directory
   \!     the history number of this command
   \#     the command number of this command
   \$     if  the effective UID is 0, a #, otherwise a $
   \nnn   the character  corresponding  to  the  octal number nnn
   \\     a backslash
   \[     begin a sequence of non-printing characters,
          which could be used to embed a terminal con­
          trol sequence into the prompt
   \]     end a sequence of non-printing characters

Para aplicar definitivo altere a variável no arquivo /home/seu_user/.bashrc