I think I get it now. To see colors in stand-alone TCCs you must have ANSI=Yes. Who provides the colors (TCC/Windows) depends on ANSIWin10.
I stumbled on one thing that misbehaved with ANSIWin10=No. I was playing with wsl (see discussion in another forum). I wondered if you get a wsl for every running linux program (answer apparently no). so in bash I issued something like
/mnt/c/apps/tc23/tcc.exe /c tl \| grepp /i wsl
GREPP is a TCCC plugin, but "tl" (tasklist wrapper) uses "wsl egrep" and "wsl sort". With ANSIWin10=No, when I got back to the bash prompt, I saw this (and I got a sound).
The same experiment from a TCC started with ANSIWin10=Yes gave no sound and ended up looking a little better.