1. One or more hardware computer-readable storage media comprising computer-executable instructions for automatically identifying outlier images in a set of images, the computer-executable instructions performing steps comprising: selecting a pixel in an image from the set of images; generating an average color value for the selected pixel by averaging color values for corresponding pixels in other images from the set of images; establishing a color value range around the generated average color value for the selected pixel, the established color value range being based on the color values for the corresponding pixels in the other images from the set of images; generating a per-pixel penalty value for the selected pixel based on a difference between a color value of the selected pixel and a threshold color value of the established color value range for the selected pixel that is closest to the color value of the selected pixel if the color value of the selected pixel is outside of the established color value range for the selected pixel; setting the per-pixel penalty value for the selected pixel to zero if the color value of the selected pixel is within the established color value range for the selected pixel; repeating, for other pixels in the image, the selecting, the generating the average color value, the establishing, the generating the per-pixel penalty value and the setting the per-pixel penalty value; generating an image penalty value for the image from the set of images based on a sum of the generated per-pixel penalty values for pixels in the image; generating a threshold penalty value based on the generated image penalty values; identifying, as the outlier images, images having the image penalty value greater than the threshold penalty value.