Microsoft had long removed the “Aero Glass” transparency style in Windows 8 RTM version by default. Whether it was a good or a bad decision is better left for personal opinion but you can get still get the limited Aero theme style transparency in Windows 8 back.
Some users and blogs had reported a trick which makes use of High-contrast Windows theme to enable Aero style transparent windows but that trick does not work anymore in RTM and final version of Windows 8. So here is a limited but working software solution using Aero8Tuner, which allows you to change settings that are hidden in Windows 8.
You can enable high-contrast theme very easily using Aero8Tuner (which is not very pleasant though). As Microsoft had removed most of the Aero transparency and functionality from Windows 8, this application gives you limited but working options. You can select and change the custom color for all windows and can even select more colors than what is offered normally from Windows Personalize menu.