Why Taller Grass Next to Added Dirt?

In my fifth year (and third video: 2020-2022: • Increased Grass Growth... 2023: • Attempting to See if S... ) I use tile painted different colors in an attempt to see if the reason I am seeing taller grass growth next to the dirt I add is due to the darker colored gravel absorbing more heat from the sun.
Experiment conducted early April to early May 2024

[@Mr__Chicken]

Is it the darker colour though? Because things that are black will absorb heat faster but dont they also disapate that heat faster too?

[@KestrelOwens]

I don't know enough about the physics to give an actual answer but that might really only be a significant factor at higher temperatures.