Python - Non capisco a cosa si riferisca l'errore

Traceback (most recent call last):
  File "tkprova.py", line 40, in <module>
    s = Slider()
  File "tkprova.py", line 34, in __init__
    self.C = RGB_color()

class RGB_color():
	RED = 0
	GREEN = 0
	BLUE = 0

	def __init__(self):
		print "RGB Setting"

	def StoreRGB(self, file_n, r,g,b):
		colors = [r,g,b]
		filem = open(file_n, 'w+')
		filem.writelines(colors)
		filem.close()


	def GetRGB(self, file_n):
		global RED, GREEN, BLUE
		filem = open(file_n , 'r')
		colors = []
		colors = filem.readlines()
		RED = int(colors[0])
		GREEN = int(colors[1])
		BLUE = int(colors[2])
		filem.close()

import Tkinter
from rgb_color import RGB_color

class Slider ():
	r=0
	g=0
	b=0

	def CheckColorRed(self,val):
		global r,g,b
		r = val
		self.C.StoreRGB('rgb.txt',r,g,b)
		print "Color(",r,",",g,",",b,")\n"

	def CheckColorGreen(self,val):
		global r,g,b
		g = val
		self.C.StoreRGB('rgb.txt',r,g,b)
		print "Color(",r,",",g,",",b,")\n"

	def CheckColorBlue(self,val):
		global r,g,b
		b = val
		self.C.StoreRGB('rgb.txt',r,g,b)
		print "Color(",r,",",g,",",b,")\n"
	
	def __init__(self):
		global r,g,b
		self.W = Tkinter.Tk()
		self.W.title("Color Selector")
		self.Red = Tkinter.Scale(self.W, orient= Tkinter.HORIZONTAL, from_=0, to=255, tickinterval=30, length=300, command=self.CheckColorRed).pack()
		self.Green = Tkinter.Scale(self.W, orient= Tkinter.HORIZONTAL, from_=0, to=255, tickinterval=30, length=300, command=self.CheckColorGreen).pack()
		self.Blue = Tkinter.Scale(self.W, orient= Tkinter.HORIZONTAL, from_=0, to=255, tickinterval=30, length=300, command=self.CheckColorBlue).pack()
		self.C = RGB_color()
		self.W.update()

	def Update(self):
		self.W.mainloop()

s = Slider()
s.Update()