edit a variable as a result of a collision

I have looked at this question for quite some time. http://answers.unity3d.com/questions/346593/editing-a-variable-from-another-script-on-collisio.html I would like to change the jumpForce variable when the player jumps off of certain materials. They are tagged with mostly colors. Here is the first script. PlayerMovement.cs

using System.Collections;

 public class PlayerMovement : MonoBehaviour
 {
     private float speed = 10f;
     public float jumpForce = 8f;
     private float gravity = 30f;
     private Vector3 movedir = Vector3.zero;
 
 
     void Update ()
     {
         CharacterController controller = gameObject.GetComponent<CharacterController> ();
 
         if (controller.isGrounded) {
             movedir = new Vector3 (Input.GetAxis ("Horizontal"), 0, Input.GetAxis ("Vertical"));
         
             movedir = transform.TransformDirection (movedir);
 
             movedir *= speed;
 
             if (Input.GetButtonDown ("Jump")) {
                 movedir.y = jumpForce;
 
             }
         }
 
         movedir.y -= gravity * Time.deltaTime;
 
         controller.Move (movedir * Time.deltaTime);
 
 
     }
 
 
 }

and the collision script. Collision.cs

using System.Collections; using UnityEngine;

public class Collision : MonoBehaviour {

 public float beigeJump = 28f;

 void OnCollisionEnter (Collision col)
 {
     if (col.gameObject.tag == "beige")
     {
         col.gameObject.transform.GetComponent<PlayerMovement>() 
             .jumpForce += beigeJump;

     }
 }

}

Thanks