At first I thought it was the light color of juvenile grass in a growth spurt. But your close up shows the plants are mature. So you've already established that it's not the nutrients, weeds or species of grass. What's left is the thatch layer. Do a core test on the green area and compare it to the yellow area. Is it the same thickness? It's got to relate to the uptake of nutrients & water. Try to count the number of grass plants in each of the areas.
I'd have thought the core aeration would have evened out the areas. Maybe you need to drag coarse sand into the core holes to help out the penetration of nutrients & water.
I've seen over managed turf that was so dependent on surface feeding that it had no roots at all. You could lift it up like a carpet. My big mowers sucked it up and shot it out the discharge chute! The customer was livid! I said "HEY! It's not my fault! I didn't over feed it!"