Example script that destroys a player when they enter a trigger, and also turns the trigger's object red.

SphereTrigger.cs

using UnityEngine;
using System.Collections;

public class SphereTrigger : MonoBehaviour {
	void OnTriggerEnter(Collider other) {
		renderer.material.color = Color.red;
		
		if(other.gameObject.tag == "Player") {
			Destroy(other.gameObject);
		}
	}
	
	void OnTriggerExit(Collider other) {
		renderer.material.color = Color.white;
	}
}