Yosemite window close button off center?
Your display is made up of pixels which are each made up of 3 subpixels, red, green, and blue. (This is the LCD part in the picture below.) Unfortunately, since red is on the left, it may look a little off center.



Here's a screenshot of the button:



and here's what it looks like on my display:



It would have been difficult for Apple to avoid this issue while still having the close button red. Graphite fixes this because the button is no longer red, and each of the subpixels is equal, so it doesn't look like it's shifted to the left.

In Mavericks, the button was a bit less saturated and a bit subtler, so that may be the reason why it seems to be a problem in Yosemite.