How to plot two list on the same graph with different colors?

[Alberto]

Dear Python Users,

I tried to plot a graph from two lists on the same graph. However, what I get is that two lists are plotted against each other. How can I plot two lists on the same graph, but with different colors?

import matplotlib.pyplot as plt

train_W = [1,2,3,4,5,6]
train_X = [1,2,3,4,5]
train_Y = [10, 20, 30, 40, 50]
train_Z = [10, 20, 30, 40, 50,25]

alpha = float(input("Input alpha: "))

forecast = []


for x in range(0, len(train_X)+1):
    if x==0:
        forecast.append(train_Y[0])
    else:
        forecast.append(alpha*train_Y[x-1] + (1 - alpha) * forecast[x-1])
plt.plot(forecast,train_Z,'g') 
plt.show()