Sarasa is the best gel pen I tried. It has a very good inkflow, the ink lasts for a long time, it glides smoothly and never dries up. You can get a case of 10 colored pens shown below or a case of 10 black pens. Most of the colors in the colored case are very good, especially dark red, dim blue and dark green; but four of them are only good for highlighting: red, orange, bright green and magenta. There is a color case with a different round up of colors, but it has a few bright colors, too. I'm not sure if it has 4 also, or fewer. Sarasa pens have a button on top that hides the pen tip inside.
The photo below shows that second variety of colored pens.