I could never quite put my finger on what was different about Seven in Time and the Rani til I had a browse through screencaps. I love that he spends a decent amount of time in his predecessor’s outfit - it’s very odd but works well. McCoy suits it - having darker hair helps, and it drowns him so he looks quite whimsical in it. But yeah. It’s the hair that’s “off” in his debut story:
It’s lovely - it’s fluffy and I want to ruffle my hand through it! - but it’s just too neat. We never see Seven’s hair this neat again (indeed, we rarely see him without a hat once he picks out his new costume).
Over the course of Season 24, his hair starts to become more and more ‘scruffy’, unkempt:
That’s the “definitive” Seven look, for me.
What’s also interesting is how Seven begins with a rough-looking hat. It’s McCoy’s own and it looks a little on the battered side:
And it’s brilliant! I love that hat.
I think it’s a bit of a shame that they later “neaten” up the Seventh Doctor (the same happened with Matt Smith - compare his hair and appearance in Series 5 to the more ‘styled’ and ‘costumed’ look of Series 6).