@ECHO OFF
SETLOCAL
SET "esc="
SET "normal=%esc%[1;33m"
SET "red=%esc%[1;31m"
SET "green=%esc%[1;32m"
:start
echo hello, are you a Robot?
:choice
echo How do you answer?
set /P c=[%green%Y%normal%/%red%N%normal%]
if /I "%c%" EQU "Y" goto start
if /I "%c%" EQU "N" goto shutdown
goto choice
:shutdown
My normal colour settings are yellow on black. The escape character is well- an escape, however it might be rendered on SO. I use editplus, which allows control characters to be entered. Other editors may allow this in other ways.
Other than that, it's simply a matter of switching the colours as desired and reverting to normal colours after showing the specials.
I've added a setlocal so that environment changes are reverted when the batch closes (this is for the general case; yours seems to be set up to exit)
I've also removed the colons in the goto statements. The only condition that colons are required here is the specific case of goto :eof which has a particular meaning.