Here is an explanation:
The thing that matters in getting a given monitor to work on a given computer is the interface. All Macs that have the standard DA-15 connector (commonly, but incorrectly, called DB-15,) use an analog signal that is compatible with the still-in-use VGA signal. All you need is a physical adapter that converts the DA-15 plug into a DE-15HD plug (commonly called a 'VGA plug'.) As long as the monitor has a high enough clock rate for the resolution and refresh rate of the computer, it should work fine. Analog monitors don't really care about the exact resolution. (Although flat panels can be a little more picky.)
In short, any modern monitor that has a 'VGA' plug should work on any computer as old as an IBM PS/2 with the original VGA, or a Macintosh II with a Macintosh II Video Card (the original color Mac video card.)
I have successfully used more than one flat panel with old Macs, most often an original Apple Studio Display (the one that came out at the same time as the beige G3, and has an old-style DA-15 video plug, so no adapter is needed to use it with an old Mac.)