Okay, I'm answering my own question: but please comment if I'm wrong or missing something.
Lets imagine looking at the copies of chromosome 11 received by my Mom and by her brother from their father. In sperm formation, we expect roughly one crossover in each chromosome, and these positions would correspond to color changes in the corresponding chromosome picture, so we'd expect two color changes comparing my Mom and her brother on chromosome 11, corresponding to the one crossover that Dad gave them. Similarly, we'd expect a few more color changes due to crossovers received from their mom.
Since there aren't many crossovers, we'd expect a good portion of half match where, say, both match on the chromosome from their Dad but not from their Mom. But: sometimes by chance the two different genomes they got from Mom will just happen to match by chance, (especially since there are only four basic DNA molecules). These would produce smatterings of green among the sea of yellow. Similarly, we would expect smatterings of yellow among seas of red, where there is no match by descent but by chance both my Mom and her brother match on one chromosome. On the other hand, we wouldn't expect smatterings of color among green bars with this explanation.
And so looking again, that's what I see. Solid green bars that aren't broken up like the yellow or red bars. And red bars are broken up by more yellow then yellow bars are broken up by green because there are two ways for a red position to happen to be a half match.
Now the only trouble is why there is an occasional yellow blip in the green bars, and I guess that's because of a mutation.