Transparency Effects in Mac OS X Interface is really cool, but too many users want to disable it. Look at the following instruction to disable or enable Mac OS X Transparency Effects.
Manage Transparency in OS X User Interface
Reduce Transparency setting exists in 10.10.x or 10.11.x only.
Go to Apple menu --> Select System Preferences --> Choose Accessibility --> Select Display from the list.
Check on Reduce Transparency, you then are able to disable or enable transparent effects in Mac OS X.