Unity-I can't seem to lerp my GameObject's Color

Question

I'm just trying to make an observer pattern program one object randomly changes color and causes a group of other objects to change the same color, but I wanted them to gradually change over 5 seconds. I'm trying lerp, but it just instantly swaps colors. I think it maybe has something to do with the lerp's starting color, because the main object is constantly shifting colors and new colors become old colors. So I need to think of how choose a starting color for the lerp. I'm not sure if this has to do with my the lerp isn't working, but it's what I'm considering. If anyone else has any suggestions, I would appreciate it. Thank you.

public class Subject : MonoBehaviour {

public float timer = 0.0f;
public GameObject[] observers;
float t = 0;


Color oldColor;

void Update () {
    t += Time.deltaTime / 5.0f;
  timer += Time.deltaTime;

  if (timer >= 10f) {
    Color newColor = new Color(Random.value, Random.value, Random.value, 1.0f);
    GetComponent<Renderer>().material.color = newColor;

    for (int i = 0; i < observers.Length; i++) {
      observers[i].GetComponent<Renderer>().material.color = Color.Lerp(oldColor, newColor, t);
    }
    newColor=oldColor
    timer = 0;
    }
  }
}

Answer 1

What Color.Lerp(Color a, Color b, float t) does is

Linearly interpolates between colors a and b by t

For example, Color.Lerp(Color.blue, Color.red, 0.5f) returns a half way interpolation between blue and red. When you say Color.Lerp(oldColor, newColor, 5) it will return newColor, because

t is clamped between 0 and 1. When t is 0 returns a. When t is 1 returns b.

So 5 is the same thing as putting in 1.

So you will need to keep a t variable somewhere that starts at 0 and increments up to 1, you put into Lerp.

For example:

float t = 0;
private void Update()
{
    t += Time.deltaTime / 5.0f; // Divided by 5 to make it 5 seconds.

    this.GetComponent<Renderer>().color = Color.Lerp(oldColor, newColor, t);
}

https://docs.unity3d.com/ScriptReference/Color.Lerp.html

EDIT

Also whats happening in your code, assuming you reset t when timer hit

1. Timer >= 10.0f
2. Lerp once
3. Reset timer to 0

. What you could do instead is something like this (i took out the observers and stuff just to make it easier to see)

float t, timer;
bool lerping = false;
Color newColor;
void Update()
{
    t += Time.deltaTime / 5.0f;
    timer += Time.deltaTime;

    if (timer >= 10f)
    {
        lerping = true;
        t = 0;
        newColor = new Color(Random.value, Random.value, Random.value, 1.0f);
        Debug.Log("Lerping!");
        timer = 0;
    }

    if (lerping)
    {
        GetComponent<Renderer>().material.color = Color.Lerp(oldColor, newColor, t);
        if (t >= 1.0f)
        {
            lerping = false;
            Debug.Log("Stopped lerping");
        }

    }
}