戻り値の受け取り、別クラス版

CoroutineSample1.cs

using UnityEngine;
using System.Collections;
using System.Collections.Generic;

public class CoroutineSample1 : MonoBehaviour
{
	void OnMouseDown()
	{
		StartCoroutine(ChangeColorCoroutine());
	}
	
	IEnumerator ChangeColorCoroutine()
	{
		var left = new WaitCoroutine();
		var right = new WaitCoroutine();

		var leftCoroutine = StartCoroutine(left.ChangeColorCoroutineWithRuntimetime());
		var rightCoroutine = StartCoroutine(right.ChangeColorCoroutineWithRuntimetime());
		
		yield return leftCoroutine;
		yield return rightCoroutine;
		
		// 待機時間の合計をログに出力
		var sum = left.waitSec + right.waitSec;
		Debug.Log(sum);
	}
} 

class WaitCoroutine
{
	public float waitSec {get; private set;}
	public IEnumerator ChangeColorCoroutineWithRuntimetime()
	{
		waitSec = Random.Range(0.2f, 1f);
		yield return new WaitForSeconds(waitSec);
	}
}