I created a new game object:
GameObject newObject = new GameObject("ObjectName");
newObject.AddComponent<RectTransform>();
newObject.GetComponent<RectTransform>().sizeDelta = new Vector2(width, height);
I'm looking for a way to add an image (script) for color purposes. How can I do it?
The same way you are adding RectTransform.
newObject.AddComponent<Image>();
You also need to add using UnityEngine.UI
to be able to find the Image component.