GUI Textures and Colliders

How do I make it so that when I step into a box or a collider that I GUITexture appears?

function OnCollisionEnter()
{
myTexture.enabled=true; //if you want it to appear suddenly. Set it to enabled = false in the inspector beforeā€¦
FadeTexture(myTexture); // If you want a fade
}

function FadeTexture(tex : GUITexture)
{
   while(tex.color.a!=targetAlpha)
   {
          //do your thing here. lerp the texture's alpha, or increase it by a fixed amount every frame, whatever suits your needs...
   }
}