Finding out that you're the lowest paid person on your team even though you do the same (or more!) work than your colleagues is a pretty discouraging discovery. If you do find out, you should definitely bring it up to your manager or if you think they're sympathetic and can do something about it. How you do it, however, is what makes the difference between better pay or a dismissal letter.
If you've found out that you're underpaid, it's likely either because someone else you work with told you, or because you did the research yourself and found that the average salary for your role at your company—or in the industry as a whole—is higher than what you're making. Now it's time to do a little homework.
Are You Really Underpaid?
The first thing you shouldn't do with this information is assume that because you're making less than your colleagues that you're underpaid. You'll need more evidence than that if you go to your manager, so before you get too angry do a little digging.