From commander Thire's EU entry:
Emphasis MineThough most clone troopers spent their accelerated formative years on storm-drenched Kamino developing under the careful watch of politically ambivalent scientists, there are two units that were notable exceptions. The red-marked shock troopers and the blue-marked 501st legion were raised and trained on Coruscant shortly following the Battle of Jabiim and increased threats to the galactic capital.
Here, "units" refers to two different legions. Is this of no consequence or a true change in meaning?