ButtonScript.cs

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

public class ButtonScript : MonoBehaviour
{
 public static bool pressing; 

 public MeshRenderer buttonMesh;
 public Light buttonLight; 
 public Color PressedColor;
 public AudioSource PressSound; 

 private Color initColor;
 private Color initLightColor;

 void Start()
 {
 initColor = GetComponent<MeshRenderer>().material.color;
 initLightColor = buttonLight.color; 
 }

 void Update()
 {
 if (Input.GetKeyDown(KeyCode.U))
 {
 pressing = true;
 buttonMesh.material.color = PressedColor;
 buttonLight.color = PressedColor;
 PressSound.Play();
 }
 }

 void OnTriggerEnter(Collider other)
 {
 pressing = true; 
 buttonMesh.material.color = PressedColor;
 buttonLight.color = PressedColor;
 PressSound.Play(); 
 }

 void OnTriggerExit(Collider other)
 {
 pressing = false; 
 buttonMesh.material.color = initColor;
 buttonLight.color = initLightColor; 
 }

}