SamyGO

I have easier solution for you!
Attach the same USB you have used for FFB , here is T-CHLCIPDEUC 2006.0 original firmware. Then power off TV. Attach this USB to tv.
Power tv on and shortly after that press and keep holding the RC button "source" and in the same time "source" on front tv panel. Wait until tv starts direct firmware upgrade procedure. The time is enough to flash firmware this way.

After success, you get preFEB firmware.

Turn TV on and hold together source on RC and source on TV panel. try many times, the pop-up window should appear.

P.s unplug tv from electricity and try the procedure

The menu color you can change later in service menu.

Have you restored your TV? Is it still rebooting? why do you take care about menu color...?