bug#34606: Emacs colors are off in screen sessions

["Clément Pit-Claudel" <cpitclaudel@gmail.com>]

On 21/02/2019 10.20, Eli Zaretskii wrote:
>> From: Clément Pit-Claudel <cpitclaudel@gmail.com>
>> Date: Thu, 21 Feb 2019 09:56:18 -0500
>>
>> Is this all as expected?  Why does changing to xterm-256color yield different results with or without ncurses-term?  If I understand correctly, the reason why TERM changes after I install ncurses-term is that this package provides the screen.xterm-256color termcap entry, and then screen acts as documented:
>>
>>        When screen tries to figure out a terminal name for itself, it first looks for an entry named "screen.<term>",
>>        where <term> is the contents of your $TERM variable.  If no such  entry  exists,  screen  tries  "screen" (…)
>>
>> Is there anything that Emacs could do differently to make things smoother?  In particular, could TERM=screen.xterm-256color behave the same as TERM=screen-256color?
> 
> Emacs on a TTY doesn't control the colors in RGB terms, it just tells
> the terminal to display color number N.  What you actually see as
> result is up to the terminfo entry and the terminal emulator, AFAIK
> mostly the latter.  So I'd suggest to dig into 'screen's
> customizations to see how to affect the colors (I customized the
> colors of PuTTY to get something I like, for example).

I don't understand. If that is the case, how can changing the value of the TERM environment variable change the colors displayed by emacs?