One additional point to add to your notion of colored links being conventions on the web. Undoubtedly, this convention is set and should be adhered to, in order to produce a more obvious design. I’d also say that as designers (and I mean that in a broad sense, not visually), we need to pay attention to designing an experience that leads a user to a call to action in a very logical and planned manner. Often times, despite the use of conventions, a bad experience design can leave a user completely confused, with no idea of what action they are expected to take. By combining conventions, such as colored links, with good, well thought out experience design, your users won’t have to think, and they’ll associate their feeling of intelligence with your product. Not a bad result!