When I go to make an edit on (e.g.) en.wp and I tab from the edit window to the edit summary and then the buttons "Save changes", "Show preview", and "Show changes" the highlighting around these buttons is far too subtle to tell what is actually selected by my browser. I dislike the candy coloring in the first place and think it's just ugly design but this is far less usable--it used to be clear which button had the focus and now it's not.
@Koavf This is an issue with underlying OOjs UI (Wikimedia's main user interface library) and its specific theme used in Monobook. With this change recently, bugs like the current one get more attention and priority, but it might still take some time till a well-working solution is found and published.
In the meantime please consider to switch your Skin und “Preferences” > “Appearance” (here link for English Wikipedia) to more modern and frequently maintained & developed Vector – the screenshot above shows the buttons in Vector skin.