You can plot several columns at once by supplying a list of column names to the plot's y argument.
df.plot(x="X", y=["A", "B", "C"], kind="bar")
This will produce a graph where bars are sitting next to each other.
In order to have them overlapping, you would need to call plot several times, and supplying the axes to plot to as an argument ax to the plot.
import pandas as pd
import matplotlib.pyplot as plt
import numpy as np
y = np.random.rand(10,4)
y[:,0]= np.arange(10)
df = pd.DataFrame(y, columns=["X", "A", "B", "C"])
ax = df.plot(x="X", y="A", kind="bar")
df.plot(x="X", y="B", kind="bar", ax=ax, color="C2")
df.plot(x="X", y="C", kind="bar", ax=ax, color="C3")
plt.show()
