The only thing I really picked up from them in game is that Fred is a bit of a dry humor guy, but Kelly and Linda felt the same. Which is a shame, because they're not the same in the books. Linda is quiet with an occasional penchant for dark humor, Kelly is a go-getter who likes being in the fight and keeping her friends alive, and Fred tries hard to not crack under the pressure of leadership. It's of course partially a consequence of them not being in books anymore where you can hear their thoughts, but also that they stop mattering to the plot after their first level. The conflict is Locke hunting Master Chief, not Osiris hunting Blue Team. Halsey begs Locke to bring John home safely, Vadam distrusts him for hunting the Demon, Cortana wants John her favorite Spartan back to her, and none of them say anything about Blue Team.