To build a system like that, you need: 1. A physical phenomenon, spectrum of light in this case. 2. An entity with a retina with light perceiving cells at the

To build a system like that, you need: 1. A physical phenomenon, spectrum of light in this case. 2. An entity with a retina with light perceiving cells at the right bandwidth. 3. A network that represents an invariant concept at that bandwidth without too many dependencies on object and context. However, there might be visual illusions that are hard to get rid of. 4. If the entity needs to describe this concept to others you need a(nother) network that maps the concept to a sequence of utterances that maps to vocal cords or muscle movements for a keyboard. 5. If the entity has to be able to reason about the concept it needs to be able to store it for longer times and have flexible ways to combine it with other concepts. 6. If the entity needs retrospection of this behavior it needs to have a representation of itself.