Camouflage and mimicry are valuable adaptations that allow creatures to hide from predators or prey, increasing their odds of survival as they are less likely to be hunted or to be spotted when hunting.
Work Step by Step
Geckos that looked more like their surroundings would be more likely to survive than those that did not. Over many generations, this would gradually be selected for until the typical gecko in this population was camouflaged. Over time, and with each generation of selection, the adaptation would become more and more developed as the best hidden geckos had the best outcomes and were more likely to pass on their genes to the next generation.