Python script failing with AttributeError: LED instance has no attribute '__trunc__'

I am currently bread-boarding two LEDs with 560 mOh resistors connected to the RPi over a ribbon cable that connects to the breadboard with a Pi Cobbler.

The problem I am getting isn't with the hardware, it's with the script. When I run it, I get this error:

led_g-r.py:11: RuntimeWarning: This channel is already in use, continuing anyway.  
Use GPIO.setwarnings(False) to disable warnings.
  GPIO.setup(GREEN_LED, GPIO.OUT)
led_g-r.py:16: RuntimeWarning: This channel is already in use, continuing anyway.  
Use GPIO.setwarnings(False) to disable warnings.
  GPIO.setup(RED_LED, GPIO.OUT)
Traceback (most recent call last):
  File "led_g-r.py", line 59, in 
    main()
  File "led_g-r.py", line 56, in main
    green.flash(3)
  File "led_g-r.py", line 33, in flash
    for flash in range(0, repeat):
AttributeError: LED instance has no attribute '__trunc__'

Can anyone see the problem in my code (included below). I wrote the script myself and I'm rather new to python so I probably will have a few problems/code that could be done better.

I wrote this with a class so that I could change around my projects with different LED configurations.

This is the code:

import RPi.GPIO as GPIO
import time       

GPIO.setmode(GPIO.BCM)

class LED:                                 
        def __init__(self, color, pin):
                self.color = color.lower()
                if self.color == 'green':
                        GREEN_LED = pin                          
                        GPIO.setup(GREEN_LED, GPIO.OUT)             
                        self.LED = 'GREEN_LED'                      

                elif self.color == 'red':
                        RED_LED = pin
                        GPIO.setup(RED_LED, GPIO.OUT)
                        self.LED = 'RED_LED'

        def OFF():                           

                GPIO.output(self.LED, False)

        def ON():
                GPIO.output(self.LED, True)


        def flash(repeat=1, length=1, cust=0):  # repeat is automatically 1
                                        # cust is automatically 0
                                        # length is automatically 1:
                                        # 1 = short-on/off for 3sec.
                                        # 2 = medium-on for 5sec. off for 3sec.
                                        # 3 = long-on for 10sec. off for 3 sec.
                                        # 4 = custom-set cust=length on in sec.
                for flash in range(0, repeat):       
                        ON()           
                        if length == '1':
                                time.sleep(3)
                        elif length == '2': 
                                time.sleep(5)
                        elif length == '3':
                                time.sleep(10)
                        elif length == '4':
                                time.sleep(self.cust)
                        OFF()
                        time.sleep(3)                            
                        ON()

        def SOS(repeat=1):
                flash(3, 1)
                flash(3, 3)
                flash(3, 1)                          

def main():                              
        green = LED('green', 18)

        red = LED('red', 23)                

        green.flash(3)                     
        red.flash(3)                          
main()

Thanks!

PS...If it helps, I can post a picture of the configuration. I also have connected my USB to TTL Console Cable so I can connect to the pi without having to use my awful screen.