以下代码段正确设置了“组合框”下拉列表中各个条目的颜色。然而，当选择并传送到CurrentText字段项目时， 所有_在下拉变化CurrentText的颜色的条目。如何在 _不 影响下拉列表的 情况下 传输要显示为CurrentText的条目的颜色？

import sys
from PyQt5.QtWidgets import *
from PyQt5.QtGui import *
from PyQt5.QtCore import *

class ComboDemo(QWidget):

    def __init__(self):
        super().__init__()
        self.initUI()

    def initUI(self):

        def combo_changed():
            for color in ('red', 'green', 'blue'):
                if color == cb.currentText():
                    cb.setStyleSheet('color: {}'.format(color))

        grid = QGridLayout()
        cb = QComboBox()
        grid.addWidget(cb, 0, 0)
        model = cb.model()
        for color in ('red', 'green', 'blue'):
            entry = QStandardItem(color)
            entry.setForeground(QColor(color))
            model.appendRow(entry)

        cb.currentIndexChanged.connect(combo_changed)

        self.setLayout(grid)
        self.show()

app = QApplication(sys.argv)
c = ComboDemo()
app.exec_()