How do I format axis ticks to be a certain color based on sign?

Question

I want my y-axis tick labels to be green when tick values are positive and red when tick values are negative.

Consider the following series and plot

Answer 1

You can accomplish this by using using the ax.get_yticklabels() and ax.get_yticks() methods of an axis...

import numpy as np
import pylab as plt
import pandas as pd
# figure data
np.random.seed([3,1415])
# create the plot
ax = plt.figure().gca()
ax.plot(pd.Series(np.random.randn(100)).add(.1).cumsum())
# change the y-axis label colors based on positive/negative
a = [ax.get_yticklabels()[i].set_color('red')  if (ax.get_yticks()[i] < 0 ) else ax.get_yticklabels()[i].set_color('green') if ( ax.get_yticks()[i] > 0 ) else ax.get_yticklabels()[i].set_color('black') for i in range(len(ax.get_yticklabels()))]

The above uses the list comprehension [a if A else b if B else c for list].