Remove Solid/Blank Images

In my work role, I need to programmatically clean up blank images mixed in with millions of usable images. For this, I turned to Python and PIL:

from PIL import Image
from sys import argv

script, filename = argv

img = Image.open(filename)
colors = img.getcolors()

if colors:
    if len(clrs) == 1:
        print str(filename)+": "+"solid color, remove"
else:
    print str(filename)+": "+"has multiple colors, keep."