The problems are potentially related did they start at the same time? Do blank pages come out ok?
The colour problem sounds like the Intermediete Transfer Belt which is in the Imaging Drum is not turning and thus smearing all colour on your page, normally this would give a messy rainbow look.
The jam could be because of the amount of toner on the paper or could just be an unrelated fuser jam.
If you look at the drum cartridge there is the main blue roller. just above this, part of the belt is visable. If you rotate the blue roller, the belt should also rotate. If it does not then inside the drum the connecting gears / levers etc will not be right.
It's not easy to service, too many springs and clips to put back together.
If you call Dell Tech Support, the will replace the drum as it has a life warranty and 300 prints is not end of life...