如何获得图片中心点的颜色值？

此主题相关图片如下：2.bmp

加入一个TextBox控件,一个按钮控件 
下列代码如何修改

: 

Private Declare Function GetPixel Lib "gdi32" (ByVal hDC As Long, ByVal X As Long, ByVal Y As Long) As Long 
Private Declare Function GetWindowDC Lib "user32" (ByVal hWnd As Long) As Long 
Private Sub Command1_Click() 
Dim Color As Long 
WindowDC = GetWindowDC(0) \'获取屏幕的设备场景 
Color = GetPixel(WindowDC, 500, 100) \'获指定点的颜色 
\'分解RGB颜色值 
R = (Color Mod 256) \'红色 
b = (Int(Color \\ 65536)) \'蓝色 
G = ((Color - (b * 65536) - R) \\ 256) \'绿色 
Text1.BackColor = RGB(R, G, b) 
End Sub

上图蓝色的色相值是多少？