Windows – How to Dump CMD Prompt Contents to File from Batch File

You could use a program like Unlocker to release the lock: http://www.emptyloop.com/unlocker/

It is a bit tricky, because you do not want the background color changing process to intercept any of your console input. You could add the /NOBREAK option to the TIMEOUT command, such that the script never reads stdin, except it still could process a <CTRL-Break> interupt, and ask if you want to terminate the script. The user could respond with Y and terminate the background process, but that could get confusing if the main process also has a running batch script. Which process gets the input?

You can redirect stdin to nul for the background process, but TIMEOUT fails if input is redirected.

I modified your auto-change-text-color.bat to use a PING delay instead of TIMEOUT, thus allowing stdin to be redirected to NUL. I also put one last COLOR command at the end to finish with a more readable color combination.

@echo off
set NUM=0 1 2 3 4 5 6 7 8 9 A B C D E F
for %%x in (%NUM%) do (
  for %%y in (%NUM%) do (
    color %%x%%y
    >nul ping localhost -n 2
  )
)
color 07

The following command is used to launch the script in the background with stdin redirected to nul:

start "" /b cmd /c "auto-change-text-color.bat <nul"

The only odd side effect is that the background process still can receive <CTRL-Break>, and it prints out the message Terminate batch job (Y/N)?, but immediately continues without waiting for input. So you can safely start a batch script in the main process, issue <CTRL-Break> and get two Terminate messages, and press Y or N knowing that only the batch script in your main process will respond (terminate or not).