Check out example codes for "how to change image color unity". It will help you in understanding the concepts better.

Code Example 1

using UnityEngine.UI;

public GameObject YourgameObjectWithImage;
YourgameObjectWithImage.GetComponent<Image>().color = new Color32(255, 255, 225, 225);

Code Example 2

image.GetComponent<Image>().color = new Color32(255,255,225,100);

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