If it is old or has been used a lot, it is probably a worn or perished rubber roller that is worth about tuppence ha'penny but will need a lot of head scratching, the right tools, a lot of patience and the biggest pot of luck you can buy. And that is if you can find (or mackle) the replacement part !
And remember that if one has gone the others (and there will be several) the others will be ready to go as well. So if you are going to replace one, replace the lot.
And before you start ask yourself this; if you manage to disassemble the mechanism, can you get it all back together again ?
Of course, someone may turn up and tell you that "all you need to do is hold the colour scan button down for ten seconds and jobs a good 'n", but I doubt it.
14:41 Sunday 21 November 2021