With the release of OSX Yosemite, Apple has taken design cues from iOS in a beautiful attempt to flatten their Mac software. With that redesign, the use of blur panes and brighter colors have taken a priority. Now we're beginning to see the transition from 3rd- party applications to this new design language.
Hover & Boxes
When a cursor hovers/clicks over these types of boxes, a blue state will occur, indicating to the user that the current box is selected. Radial buttons are designed with a simple circle to indicate what has been selected, while the checkmark serves for multiple options that can be selected.
For text-input boxes, the use of color gives the user a sense as to when input is correct and incorrect. The green state highlights boxes that have correct information entered, while the yellow state highlights mistakes like passwords that are too short. The red highlight indicates incorrect information entered.
Personally, I’m all for the redesign. The iconography of Mac OS X Yosemite are a step-up from the iOS counterparts, Helvetica is a beautiful system font provided you have a Retina display, and most importantly, the feeling of OS X hasn’t vanished. There’s still plenty to be done in regards to polish, and the heavy blur effects are pretty taxing, but in time it’ll surely get better.