At the time I wrote the post, I was still ecstatic over the discovery of this wondrous innovation. Now, after I have had a chance to use more than just the yellow one, I'm going to reply with the sage advice won from experience.
These are the best highlighters I have ever used, with one small exception.
The blue one is awful. After I took the following picture, I threw the blue one away.
The purpose of a highlighter is to draw attention to things. The four other colors are brilliant and obvious.The blue one can barely be seen on paper.
If anything, the blue shows up better in the above picture than it does in person.
I now understand why I couldn't find the five color set in stores. If you are going to buy them, go with the four pack. It has yellow, orange, green, and pink. All four of these colors are vibrant and easy to see. Don't spend the extra money to get the blue one. It is not worth it.