Select colour then change texture

I'm looking to do a colouring book type scene where the user clicks the colour they want, then when they click a part of the model it colours it with that selected colour. I've seen this script:

 var a : gameobject;
 a.renderer.material.color = Color.blue;

Which I can link to a Raycast script but I'm not sure how to go about selecting the colour and then implementing it when the model is clicked.

I also found the following script:

 #pragma strict
 
 private var ray : Ray;
 private var hit : RaycastHit;
 private var selectedColour : GameObject;
 
 function Start () {
 }
 function Update () {    
 if(Input.GetMouseButtonDown(0)){
 ray=Camera.main.ScreenPointToRay(Input.mousePosition);
 if(Physics.Raycast(ray,hit)){
 if(hit.transform.name == "CubeRed"){
 selectedColour = GameObject.Find("Cube");
 }
 if(hit.transform.name == "Cube"){
 selectedColour.renderer.material.color = Color.red;
 }
 }
 }
 }
 

This script finds the cube when the colour button is clicked, then applies the selected colour to the cube when the cube is clicked. A little closer but still some major problems.

Firstly, when I add more colours to the script, it doesn't function, only takes into account the last colour specified, despite being on separate buttons.

Secondly, I don't want the script to look for a certain object, I want it to be applied to any of the objects I click after that.

Any ideas? Thanks in advance