Andrew, I finally got around to answering another one of your questions…
Jenny quickly losing the hair dye in episode 1 of Tomorrow's End! A production decision? I always assumed it was because Melissa Marshall had asked not to bother with the purple rinse!
I thought that was the likely reason too, but another possibility occurred to me. Maybe the dramatic change to Jenny’s hair was intended to be a visual reflection of her character’s development in the second series?
In the first series, Jenny’s temper was much shorter, and she was channeling her unhappiness about her life situation (her life dramatically changing due to her parents divorce, moving interstate, and being treated like a misfit by the girls at her new school) into being rebellious and bossy, and she would regularly vent her frustration at Petey and her mother. And instead of attempting to fit in with the crowd at school, Jenny took revenge on Maria, and defiantly and proudly presented herself with her punk look of purple, backcombed hair.
But after making friends with Alana and and after quickly accepting James as Irene’s boyfriend (initially she was unhappy about their relationship, but after James’ science knowledge came in useful when the Kelly’s rescued Alana from Silverthorn’s house, she was warmer towards him) Jenny’s persona softened a bit. Then, after returning to 1990 at the beginning of the second series, Jenny didn’t re-dye her hair, and neither did she bother doing the big backcombed styles any more.
Her softer hairstyle also may have reflected her character’s more obvious vulnerability in the second series when she was in 2500. Suddenly the roles were reversed- in the first series, Alana was the fish out of temporal water, and it was Jenny who took charge helping her, but in 2500, Jenny was the scared stranger who had no idea how things worked in that time. Alana meanwhile, by this time, had become more assertive. And something I also noticed in Tomorrow’s End was how protective Jenny was of her little brother. I am sure she always had cared about him, but her concerns were less obvious in the first series when she was frustrated and shouting at him, and calling him stupid, a mutant, etc.
I guess it’s a question to ask Melissa Marshall if any of us manage to get in contact with her!
Although I see that whoever wrote one of them misidentified Tulista 
If so, I might be tempted…