I found pretty difficult to distinguish between an highlighted and a non-highlighted question on the Arduino site. Is it just me?
Unfortunately we can't change that. All Stack Exchange sites use the same design during their beta phase. If/when we graduate to a full site, we'll get a custom design.
With that said, the difference between highlighted and non-highlighted seems reasonably clear to me. Perhaps you need to adjust some display settings on your system?
Alternatively, you could use a browser add-on which lets you write a script to modify the design automatically on-the-fly (e.g. GreaseMonkey).