Color extraction

[rland93]

Our suggestion is to do k-means to find color blobs

Largest color blob is the shape color
Next largest is the letter color
Next largest is the background color

Then find those colors and turn them into perceptual color names "red" "green" "blue" etc.

For RGB -> Perceptual color names, search around for existing libraries.

[rland93]

Scikit-learn has an excellent plug and play K-means clustering algorithm.

[rland93]

First Prototype in fb8cc0c

I think we can improve these results a bit:

https://arxiv.org/abs/1101.0395 is a good place to start.

Leaving open for now to store color stuff in this issue.