What's the best way to show that a link without the standard underline is clickable?

1. How do I show a clickable link?
2. Should links be underlined by default?
3. Why are some hyperlinks underlined?
4. What Colour should links be?

How do I show a clickable link?

Symbols and Icons

When using icons for links, make sure icons are instantly recognizable. Unless you have a really strong resemblance icon or an icon that has become standard, it should be combined with another visual cue, such as a text label, to indicate clickability.

Should links be underlined by default?

Summary: Textual links should be colored and underlined to achieve the best perceived affordance of clickability, though there are a few exceptions to these guidelines.

Why are some hyperlinks underlined?

Underlining Pros

Links are easy to find because users understand that underlined text means that it's a link. The underlining draws their attention.

What Colour should links be?

By default, a link will appear like this (in all browsers): An unvisited link is underlined and blue. A visited link is underlined and purple. An active link is underlined and red.