Can you be more specific? Flashing red THEN green is normal startup procedure. Flashing between red and green all the time is a different matter and suggests something is wrong. I get this when my throttle trim is barely low enough and fluctuates between OK and not OK. I also get this when I don't fully extend my Tx antenna and reception was bad with all sorts of interference. But then in that case, the servos would jitter and I'd know what I did wrong. So questions for you:
- do the servos jitter?
- do the servos respond to your Tx input?
- do the flashing (or at least its flashing rate) change when you change throttle input?
- does it ever flash green 3 times (about 1 flash per second, no red in between)?
If none of the above, your Tx/Rx are not even talking.
Unplug the motors. Try again and then try switching OFF the Tx. Make sure the motors are not plugged in. Anything changes?