I understand Black as a color. Countries as USA, China and India praise Whiteness skin and there is not the same race, but all praise Whiteness...
People praises what is an external sign of wealth and power. A lot of civilization praise "light skin" not because White > Black, but because the common population works in the farms and get sun tan. So, a lighter skin color means that people do not need to work farms to survive, and might be wealthy. They also praise "obesity" for the same reason: nobility can eats a lot while the common people were facing undernutitrion.
In most place around the world, this is still valid.
But, now you see that in most "white" country, people praise "dark skin" and "skinniness" now. Why? Because, due to industrial revolution and later on, the common people are working more and more inside, like in factory, in office... so they cannot get a tan because they are working inside during the day. Also, even if they do not face undernutrition anymore, they are facing malnutrition now. Healthy food suddenly became expensive, so common people buy low quality food and get fat. Having a tan (so having a darker skin from a white guy) is now synonymous of a guy that can afford some sunlight, so being able to go on vacation or having free time during work hour. No wonder why some people are painting their faces in orange to fake a tan: because it is now a sign of "wealth and power".
Nobody is denying that racism exist. It exists, and this issue needs to end: equality for everyone. But I don't know what are you trying to say with the Olmec.
Pigment for painting were not as common as today. I mean, whe used to put mummy in a blender so we can have the "Egyptian Brown" pigment, and some pigment were expensive. Never wondered why almost no flag feature the color "purple"? Because that color is that rare and expensive.
Dark pigment tend to fade away more quickly in sunlight. On your Olmec picture, we can clearly see that the bottom and the left of the picture faded away more easily. Your black guy has white legs, while having the yellow more "golden", red more "bloody" and the blue more "turquoise".
I understand that this issue is important for you. But finding racism on matter that is easily explained by other cause will harm you more and the cause you defend than helping you. Plus: we know so little about the Olmec society. How can we deduce their ideologies, their policies or even their tastes when we didn't figure out the basis of their religion(s?), how they gained influence or decline, even their actual language (Mixe? Zoquean? Both?) and ethnicity!