How do I change between the three colors?

The barrel switches between the green, pink and yellow tips, so you rotate or slide to the color you want. Each color has its own tip.

What kind of line does the chisel tip make?

A chisel tip gives a wide stroke when held flat and a thin underline when held at an angle. That makes it usable for highlighting whole lines and for underlining.

Is this one highlighter or a pack?

It is one tri-color highlighter. The three colors are green, pink and yellow in a single body.

Does it work for left-handed writers?

A chisel tip can be angled either way, so left-handed writers can use it. Fast highlighting may smudge on some paper, as with most highlighters.

Is it good for bulk orders or events?

It is a practical giveaway or classroom item because one pen covers three colors. Buyers ordering in quantity should confirm the ink colors and tip style they want.