In older EU material, it was explicitly shown that each suit of Mark-V the Spartans received was identical. Spartans all having identical suits of armor (well, each suit of a given Mark was identical, anyway) was the rule for the longest time, but it's become increasingly common to have them all be unique little snowflakes with their own sets of custom armor. 343I kind of waffles back and forth on this. The opening cinematic of Halo 4 has all the Spartans wearing identical armor (though it's all inexplicably the new set of armor the Chief magically received while in cryo) as does the new cover of The Fall of Reach, but then you get other material like the Forward Unto Dawn miniseries, The Package from Legends, and these terminals which all have the Spartans wearing unique custom armors.