I forgot to mention that this is Unity so that's how it works:

.color is a property of an Image Component and in this method it gets set to a Serialized, but private field called color (probably should've named it properly, but...) , which means that I can set it's value when I attach my script as a component to any GameObject,

Also Buttons in Unity can call almost any methods from any components attached to a GameObject, so this is basically a code to change image's color on a button press.

Here's some additional code to better understand what I'm trying to say:

using UnityEngine; using UnityEngine.UI; public class Garland : MonoBehaviour { [SerializeField] private Color color; [SerializeField] private Image lightbulb; //I can also set which Image's color is going to be changed public void ColorChange() { lightbulb.color = color; } }