This video by Envatio shows you how to do it: http://www.youtube.com/watch?v=NKwKcVL8ARg

Basically OnTriggerEnter()you can set the GUITexture enabled property to true.

var completedImage : GUITexture;

function Start() {
    // hidden by default
    completedImage.enabled = false;
}

function OnTriggerEnter() {
    completedImage.enabled = true;
}

Pls help me in the below problem:

when the player collides with the enemy ball the player have to lose one if his life and need to be to be displayed the lives left using gui text?