If you want a skin with an easy to use installer for Windows 8.1 that automatically matches taskbar color with Start Menu color, set the transparency or opacity etc, then go here and download the Winaero Skin 2.0: http://winaero.com/blog/get-the-best-looking-start-menu-for-classic-shell-4-with-winaero-skin-2-0/
Note: If you want to manually disable Taskbar transparency, that setting is on 'Windows 8 Settings' tab in Windows 8/8.1. If you made your Taskbar non-transparent, you would obviously want to make the Start Menu non-transparent too. To disable the Start Menu transparency manually, go to the Skin tab to disable it for that particular skin.Fellow users, in case you don't know, Classic Shell 3.9.3 added a new setting to override the glass color used by the Start Menu when using glass/transparency based skins. This setting is on the Menu Look tab called Override Glass Color. We can customize 3 parameters: the actual color expressed in standard RGB/HSL values, the glass intensity and the color blending. This setting is useful because for each new release of Windows, Microsoft tweaks Aero Glass and then the Start Menu skin glass color no longer matches with the Taskbar color unless you do some tweaking again.
Changing the Glass Color setting will let us change the shade so it more closely matches the taskbar shade but the problem is that the color becomes static once you change it, it doesn't change automatically when taskbar color changes. So I recommend you check Override Glass Color but leave the Glass Color setting alone (don't try to pick a custom color to match the Taskbar shade). Instead, since we have manual controls to adjust the intensity and blending, tweaking these 2 values will allow us to make the Start Menu more accurately match the Taskbar's shade. The need to use custom skins or tweak the skin bitmaps using Resource Hacker has therefore lessened.
Here are the specific values of glass intensity and color blending which I have experimented with and observed to come close to the Taskbar color. Windows release | Start Menu skin & Taskbar transparency | Classic Start Menu skin | Glass Intensity | Color Blending |
Windows 8.1 | Off | | 80 | 10 |
Windows 8.1 | On | | 100 | 70 |
Windows 8/8.1 | Off | Windows 8 skin (built-in) | 65 | 45 |
Windows 8/8.1 | On | Windows 8 skin (built-in) | 70 | 50 |
Windows 8 | On | Windows Aero skin (built-in) | 100 | 100 |
Windows 7 | On | Windows Aero skin (built-in) | 40 | 100 |
Note these are just my experimental values which I've found to make the Start Menu color match the Taskbar color (with the right transparency settings checked in the skin and for the Taskbar from the Start Button tab).
I am posting this so you can get a shade closer to the taskbar color quickly. You're welcome to post your own observations for whichever OS you use, transparency setting, skin, intensity and blending etc which makes the color match.
If you are using the paid Aero Glass mod (http://www.glass8.eu/) along with the Windows Aero skin, then you just need to enable the setting "Enable Aero Glass" from the Menu Look tab, no adjustments to override glass color should be necessary to match the taskbar.Just as an example, this is the unreadable mess that you can get when there is too much transparency. You don't want that!