Notes about Chell in the Developer's Commentary
"NEW CHELL"
"[Realm Lovejoy] We thought of making a whole new character for Portal 2, but we didn't want to lose the relationship between GLaDOS and Chell that began in Portal 1. Once we decided to stay with Chell, we wanted to improve her look: updating her leg springs and jumpsuit to have a more functional design. At the same time, we didn't want players to not recognize her, so we kept a lot of the iconic elements like the color orange. She has folded down her jumpsuit to show she has essentially rolled up her sleeves and shed some of the Aperture label...she is awake again to test, but stronger and more determined than ever."
"[Realm Lovejoy] We thought of making a whole new character for Portal 2, but we didn't want to lose the relationship between GLaDOS and Chell that began in Portal 1. Once we decided to stay with Chell, we wanted to improve her look: updating her leg springs and jumpsuit to have a more functional design. At the same time, we didn't want players to not recognize her, so we kept a lot of the iconic elements like the color orange. She has folded down her jumpsuit to show she has essentially rolled up her sleeves and shed some of the Aperture label...she is awake again to test, but stronger and more determined than ever."