Spinner appears in season one with a simple, short gelled hair. Still in middle school in season one, he went on to season two with a clean-cut hairstyle, but with less body weight, which he'd lost during the summer before high school. In season two, he bleaches his hair blond, but still uses gel. Marco appears in season two with really short, gel-less hair. His hair is decidedly simple and well groomed from the onset, as quiet as his first episode, where he had no speaking lines.
During season three and four, Spinner emulates indie rock band hairstyle - messy and long. In season three, his hair was long and curly, more like a girl's short and curly hair that doesn't go past the neckline. In season four, he wears it straight, but still rather long and resembling a girl's haircut. Marco's haircut in season three is short and wavy and evenly layered. In season four, he wears it longer and straight, but still layered.
In season five, Spinner has a manlier cut with his hair at a peak in the middle. It is short and neat like his first season hairstyle, and his non-appearance for most episodes of season six. In season five, Marco owns up to his gay sexuality to a live audience with his father in it. Marco wears long, wavy hair. In season six, Marco has his hair slicked back and short, sometimes with bangs and a manly crest out back.
Spinner goes from short and clean hair to short and curly to bald, after he learned that he had cancer and had to shave his head. He grows his hair back short in subsequent episodes. Marco wears his hair short, sometimes showing signs of needing a trim. He works as a student teacher, which may be the reason for this functional hairstyle that needs maintenance.