Colors the particles will cycle through over their lifetime.

Currently you cannot directly modify a single index of this array. Instead, you need to grab the entire array, modify it, and assign it back to the Particle Animator.

	// How to properly change colorAnimation Colors via scripting
	// Attach this script to a GameObject that contains a legacy particle components
	function Start () {
		var particleAnimator : ParticleAnimator = GetComponent(ParticleAnimator);
		var modifiedColors : Color[] = particleAnimator.colorAnimation;
		modifiedColors[2] = Color.yellow;
		particleAnimator.colorAnimation = modifiedColors;
	}

using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
    void Start() {
        ParticleAnimator particleAnimator = GetComponent<ParticleAnimator>();
        Color[] modifiedColors = particleAnimator.colorAnimation;
        modifiedColors[2] = Color.yellow;
        particleAnimator.colorAnimation = modifiedColors;
    }
}

import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

	def Start() as void:
		particleAnimator as ParticleAnimator = GetComponent[of ParticleAnimator]()
		modifiedColors as (Color) = particleAnimator.colorAnimation
		modifiedColors[2] = Color.yellow
		particleAnimator.colorAnimation = modifiedColors