finally i managed, to log as tc user (green) and as user root (red).
So, 3 small things should be updated in /etc/profile:
1. proper comment of # Light red (not green) and blue colored prompt. 
2. activate (uncoment) first PS1 line 
3. comment out second PS1 line. 
# Prompt format for Ash (Bash use /etc/bashrc).
if [ "`id -u`" -eq 0 ]; then
    # Light red and blue colored prompt.
    PS1='\e[1;31m\u@\h\e[0m:\e[1;34m\w\e[0m\# '
     #PS1='\u@\h:\w\# ' 
2 things in /home/$user/.profile: 
1. comment out first PS1 line. 
2. activate /insert second  PS1 line# Environment variables and prompt for Ash SHell or Bash. Default is a classic prompt.
# PS1='\u@\h:\w\$ '
PS1='\e[1;32m\u@\h\e[0m:\e[1;34m\w\e[0m\$ '
for ~/.profile is no problem, because it can be saved in mydata.gz 
but for /etc/profile, maybe a remaster is in need. or else boot parameters "nologin +superuser" (aka root) has no red color, because /etc/profile is sourced imediatly after /init, no chance to be (eventually) restored from mydata.gz also. I did a remaster and is working.
Regarding login as root, staring as tc-user in a aterm-shell in Xorg, is OK. (my mistake, sorry).
The proper command I should issue is:tc@box:~$ sudo login -f root
   ( '>')
  /) TC (\   Core is distributed with ABSOLUTELY NO WARRANTY.
 (/-_--_-\)           www.tinycorelinux.net
root@box:~# PS: neither tc-user, nor root-user need a password, it works without both passwords.