In meiosis I, the pair of homologous chromosomes separate from each other so that the entire red-long homolog will move one direction and the entire yellow-long homolog will move in the other direction.
If a cell ended up with both homologs, that would be the result of nondisjunction. The gametes formed from that cell will up with 2 copies of the long chromosome. The gametes formed from the other cell from meiosis I will end up with no copies of that chromosome.