如何在运行时更新数据存储在主应用程序类的变量中的kivy标签颜色

from kivy.app import App
from kivy.uix.label import Label
from kivy.uix.boxlayout import BoxLayout
from kivy.properties import StringProperty, ListProperty
from kivy.lang import Builder

Builder.load_string('''
<MyLabel>:
    color: root.label_color
    Label:
        text: root.label_text
''')

class MyLabel(BoxLayout):
    label_text = StringProperty("Hello World")  # 标签的文本
    label_color = ListProperty([1, 0, 0, 1])  # 标签的颜色，RGBA格式

class MyApp(App):
    def build(self):
        label = MyLabel()
        self.update_label_color(label)
        return label

    def update_label_color(self, label):
        # 在此处编写更新标签颜色的逻辑
        label.label_color = [0, 1, 0, 1]  # 更新标签颜色为绿色

if __name__ == '__main__':
    MyApp().run()