Python散景：同一行上有多个颜色段

import numpy as np
from numpy import vectorize
import pandas as pd
from bokeh.plotting import figure,show,output_file


def f(x):
    return 2 * x


def color(x):
    if x < 20:
        return 0
    if 20 <= x < 60:
        return 1
    if 60 <= x < 80:
        return 0
    else:
        return 1


v_color = vectorize(color)
x = np.arange(0,100,1)
data = {'x': x,'y': f(x),'colors': v_color(x)}
df = pd.DataFrame(data=data)
# print(df)

p = figure(title="Line example")

p.line(df['x'],df['y'],legend="y=f(x)",# line_color="tomato",line_color="olivedrab",line_width=2)

p.legend.location = "top_left"

output_file("basic_line_test.html",title="line plot example")

show(p)  # open a browser

基本上该行应该有一种颜色,当’colors’列为0时,我们会说’olivedrab’,当值为1时,可以说’tomato’.
我怎样才能做到这一点？