Light has always existed in the known universe. Presumably, these proto-organisms were drawn to it to gather energy, and as such, the ones who could track it fared better. Problem with things is that people forget that terms are arbitrary. Colors are completely a creation of human minds. And it's not..."Luck". It's a combination of favorable genetic changes. Early lifeforms can do things like that with remarkable speed, but the higher you go in the complexity, the slower the changes manifest.