Make iMac file structure more like windows
If you are referring to the color of the folders in OSX, unfortunately Apple thinks they should be blue. You can use different views to make them nearly any size you like, especially if you choose the icon view. 

However, if you want to change the color of the folders, I recommend an app called Folder Magic, that allows you to change the folders to any color you wish:

https://itunes.apple.com/us/app/folder-magic/id647731944?mt=12