There are many posts about the 28BYJ-48 around here, its a 5-wire unipolar small
low-power stepper. The red wire is common and its normally (or exclusively) 5V
windings I believe. The driver is a multiple darlington driver chip, probably
the ULN2003 or similar, and here's a useful looking page I found by googling
"28byj-48 arduino":