Just a brief update to indicate that the opsin function and evolution module is up in its initial-release form here:

Opsin: How mutations add functionality

The heart of this module is interactive software that lets students ‘mutate’ the gene sequence for the human red-sensing opsin protein and discover how easily it becomes a green-sensing opsin… recapitulating the evolutionary ‘re-discovery’ of this ability in old-world primates.

Posted material doesn’t cover the critical step of gene duplication yet; provided references are primarily raw materials for investigating how mutation can lead to altered function. In this case, that means how a green-detecting opsin is simply a red-detecting opsin with some mistakes in it.