How do you make a link obvious?
Shades of blue provide the strongest signal for links, but other colors work almost as well. As always, when using color to signal information, you should provide redundant cues for color-blind users. Making unvisited links brighter and more luminous than visited links will usually accomplish this goal.
How do you indicate clickability?
Summary: Whether you adopt a flat-design style or not, interactive components must retain sufficient cues to suggest clickability. Signaling clickability with cues such as borders, color, size, consistency, placement, and adherence to web standards can give interactive components the proper look.