Look at this printed report. Does it say "Default Settings" or list a standard IP address? If so, the reset was successful.
The light will cycle through colors (typically Purple → Blue → Red). To Calibrate : Release the button when the light flashes xprinter xp-420b reset
Before diving into the "how," it is important to understand the "why." Resetting a printer restores it to its factory default settings. This is a drastic step, but it solves a specific set of problems that standard restarts cannot. Look at this printed report