Button positionButton = mDialog.getButton(AlertDialog.BUTTON_POSITIVE);
            positionButton.setTextColor(ContextCompat.getColor(NewPaymentActivity.this, R.color.red_tips));
            Button negativeButton = mDialog.getButton(AlertDialog.BUTTON_NEGATIVE);
            negativeButton.setTextColor(ContextCompat.getColor(NewPaymentActivity.this, R.color.gray9));

或者

    <!-- 自定义Dialog显示风格 -->
    <style name="AlertDialogCustom" parent="Theme.AppCompat.Light.Dialog.Alert">
        <!-- NeutralButtonStyle -->
        <item name="buttonBarNeutralButtonStyle">@style/buttonBarNeutral</item>
        <!-- NegativeButtonStyle -->
        <item name="buttonBarNegativeButtonStyle">@style/buttonBarNegative</item>
        <!-- PositiveButtonStyle -->
        <item name="colorAccent">@color/colorPrimary</item>
    </style>

    <style name="buttonBarNegative" parent="@style/Widget.AppCompat.Button.ButtonBar.AlertDialog">
        <item name="android:textColor">@color/black3</item>
    </style>

    <style name="buttonBarPositive" parent="@style/Widget.AppCompat.Button.ButtonBar.AlertDialog">
        <item name="android:textColor">@color/colorPrimary</item>
    </style>

    <style name="buttonBarNeutral" parent="@style/Widget.AppCompat.Button.ButtonBar.AlertDialog">
        <item name="android:textColor">@color/black3</item>
    </style>


 <style name="AppThemeCompat" parent="Theme.AppCompat.Light">
      
        <item name="alertDialogTheme">@style/AlertDialogCustom</item>
    </style>