Color tempColor = gameObject.renderer.material.color; //Временная переменная
tempColor.a = 0.5f; //устанавливем прозрачность на 50%
gameObject.renderer.material.color = tempColor; //Присваиваем новый цвет материалу на объекте

using UnityEngine;  
  using System.Collections;  
  [RequireComponent(typeof(Rigidbody))]  
  public class PlayerController : MonoBehaviour    
  {  
    private IRagePixel ragePixel;  
    public float jumpSpeed = 500.0f;  
    public float playerSpeed = 5.0f;  
    public bool groundet;  
       
    void OnCollisionEnter(Collision floor)  
    {  
     if(floor.gameObject.CompareTag("floor"))  
     {  
      groundet = true;  
     }  
    }  
       
    void Start()  
    {  
      ragePixel = GetComponent<RagePixelSprite>();  
    }  
    void Update()  
    {  
     if(Input.GetKey(KeyCode.A))  
     {  
      ragePixel.SetHorizontalFlip(true);  
      ragePixel.PlayNamedAnimation("run",false);  
      transform.Translate(new Vector3(-playerSpeed,0,0) * Time.deltaTime);  
     }  
     if(Input.GetKey(KeyCode.D))  
     {  
      ragePixel.SetHorizontalFlip(false);  
      ragePixel.PlayNamedAnimation("run",false);  
      transform.Translate(new Vector3(playerSpeed,0,0) * Time.deltaTime);  
     }  
     if(Input.GetKey(KeyCode.Space))  
     {  
      if(groundet == true)  
      {  
      groundet = false;  
      rigidbody.AddForce(new Vector3(0,jumpSpeed,0));  
      }  
     }  
     else  
     {  
      ragePixel.PlayNamedAnimation("stay",false);  
     }  
     if(groundet == false)  
     {  
      ragePixel.PlayNamedAnimation("jump",false);  
     }  
         
    }  
  }