We have no idea what was the original skin colour of (modern) humans . Early modern humans could have been as light as San Bushmen, or as dark as South Sudanese, or even similar to Amerindians (ie, intermediate between "light" and "dark"). We just don't know yet. Also, many experts believe dark skin has some correlation to the rates of polygyny in a population. For example, West Africans have one of the highest rates of polygyny in the world and are also one of the darkest populations in terms of skin colour. The opposite can be said of most European populations. This map may be of great help:
And to say the earliest modern humans looked " Negroid" is odd if we take into account the earliest "Negroid" remains which are only 7,000 years old (see Asselar Man). In fact, the Upper Paleolithic African specimens we have to date cluster with UP Eurasians and not with modern Africans (see Hofmeyr skull at 36,000 kya).