ParticleSystem.TrailModule.colorOverTrail

Description

The gradient controlling the trail colors over the length of the trail.

See Also: MinMaxGradient.

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour
{
    private ParticleSystem ps;
    private Gradient gradient = new Gradient();
    public bool swapColors = true;

    void Start()
    {
        ps = GetComponent<ParticleSystem>();

        var main = ps.main;
        main.startSize = 0.1f;
        main.startLifetime = 1.5f;

        var trails = ps.trails;
        trails.enabled = true;

        var psr = GetComponent<ParticleSystemRenderer>();
        psr.trailMaterial = new Material(Shader.Find("Sprites/Default"));
    }

    void Update()
    {
        var trails = ps.trails;
        if (swapColors)
        {
            gradient.SetKeys(
                new GradientColorKey[] { new GradientColorKey(Color.blue, 0.0f), new GradientColorKey(Color.green, 1.0f) },
                new GradientAlphaKey[] { new GradientAlphaKey(1.0f, 0.0f), new GradientAlphaKey(1.0f, 1.0f) }
            );
        }
        else
        {
            gradient.SetKeys(
                new GradientColorKey[] { new GradientColorKey(Color.green, 0.0f), new GradientColorKey(Color.blue, 1.0f) },
                new GradientAlphaKey[] { new GradientAlphaKey(1.0f, 0.0f), new GradientAlphaKey(1.0f, 1.0f) }
            );
        }

        trails.colorOverTrail = gradient;
    }

    void OnGUI()
    {
        swapColors = GUI.Toggle(new Rect(25, 25, 200, 30), swapColors, "Swap Trail Colors");
    }
}