Yup, in fact setting a color to #RRGGBB in software doesn't mean very much. Okay, you asked for 100% red, but what is "100% red", exactly? It depends on how goo

Yup, in fact setting a color to #RRGGBB in software doesn't mean very much. Okay, you asked for 100% red, but what is "100% red", exactly? It depends on how good the monitor is, and whether the calibration is good or not. That's where you need measurement and calibration. You can easily see the need for it if you compare multiple displays like a monitor, laptop and cell phone showing the same picture. They're quite likely to be noticeably different. And printing uses a completely different color system (CMYK), so things get even more interesting there.