DJW - The detailed understanding of the specific genetic mutations that tweek light sensitivity is really amazing. It's a brilliant example of science at its best.
I don't know the answer to your question about human differences. It's entirely possible. The thing to keep in mind is that mutations are random but selection is not. In the case of birds an ability to see particular colours has a selective advantage so it tends to survive into future generations. A human who has a similar mutation is no more likely to prosper or have more offspring than one who doesn't, So this mutation might disappear just as quickly or continue for a few generations.