Well in Windows 8.1, Microsoft made the taskbar more transparent than it was in Windows 8.0. And the Classic Shell skins remained the same which may be why you are seeing a big difference in shade. You could try the Winaero Skin 2.0:
http://winaero.com/blog/get-the-best-lo ... -skin-2-0/ but note that it matches the Taskbar color only with the opaque setting. With transparent Start Menu and Taskbar, the shader is closer than Classic Shell's built-in skin but not an exact match. If it was an exact match, then the Start Menu won't remain readable if a window with text comes behind it. Although the Taskbar is more transparent in Windows 8.1, it can afford to do so because it is always on top of other windows by default and doesn't have to appear on top anything else. It doesn't make sense to make the Start Menu that much transparent.