如何更改进度条kivy的颜色

from kivy.app import App
from kivy.uix.progressbar import ProgressBar
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.label import Label

class CustomProgressBar(BoxLayout):
    def __init__(self, **kwargs):
        super(CustomProgressBar, self).__init__(**kwargs)
        self.orientation = 'vertical'
        
        # 创建进度条和标签
        self.progress = ProgressBar(max=100)
        self.label = Label(text='0%')
        
        # 将进度条和标签添加到布局中
        self.add_widget(self.progress)
        self.add_widget(self.label)

class MyApp(App):
    def build(self):
        return CustomProgressBar()

<CustomProgressBar>:
    progress:
        background_color: 1, 0, 0, 1  # 设置进度条的背景色为红色
        bar_color: 0, 1, 0, 1  # 设置进度条的前景色为绿色