Reality, as it usually does, turns out to be more complicated than the simplicity of the linkage rule.  Because linked genes can become unlinked.

During formation of male and female gametes, the sex cells undergo a special kind of cell division called meiosis.  The outcome of this is the production of cells with just a single set of chromosomes.  In our imaginary plant, this means pollen and egg cells where n=2.

During meiosis the genetic pack is shuffled.  Each chromosome seeks out the corresponding member of the other set (its homologue) and, by breaking, crossing over and reforming, genes are exchanged.

This means that sometimes G1 red will become linked with G2 blue (and G1 blue with G2 red).  Geneticists refer to making new gene associations like this as recombination.  Recombination is a way of improving the fitness of the progeny.

So we have to qualify the law of linkage to take into account crossing-over.  Notice that the chances of two linked genes becoming unlinked will change depending on how far apart they are on the chromosome.