The difference in band support between China OnePlus One and the International version...All 3 local telco bands are supported on both China and International sets...
Below is the guide on how to flash Color OS to CM...
download this file...
https://www.androidfilehost.com/?fid=95747613655046106
Method as follow.
1, Download and copy the firmware to your phone.
2, Put your oneplus one into recovery mode and there are two choices.
Method:
(1) Press and hold the power button until you see a screen asking to power off or restart the phone.
Select 'Restart' and then press and hold the "down volume key" to enter the official recovery mode.
(2) Power off the phone and immediately hold down the "power button" and "volume down key" and let go all the buttons until you feel the vibrate from the phone.
(3) Use your fingers click the "English"
(4) Choose "Install from SD" to install the firmware file from the location where you stored the file that is uploaded.
(5) Find the firmware you downloaded and click Yes to start the flash.
(6) Flashing in progress and please wait for few seconds.
(7) Choose "reboot" to restart the phone after completion of flashing. You can also wipe cache if you want before rebooting.
You can look for toolkit for your computer to flash back to stock color/cm, unlock or lock bootloader and root...