I want prims to change change color when soundloop is on

I got this nifty script that plays soundloops, menu-driven.
Now I want to the prims to change color when soundloop is on/off.
So the user does not have to guess or listen which prim is on or off.
How do I do that?

|As long as you know how long each sound clip is its just a case of setting the required colour when you start the loop playing, a sleep for the required length of time and then setting the colour back again

float length = 5.0;
string clip = "my sound clip";
vector off = < 1., 1., 1.>;
vector on = < 1., 0., 0.>;
default
{
    state_entry()
    {
         llSetColor(off, ALL_SIDES);
    }

    touch_start(integer total_number)
    {

         llPlaySound(clip, 1.0);
         llSetColor(on, ALL_SIDES);
         llSleep(length);
         llSetColor(off, ALL_SIDES);
    }
}

I'm on it.
Thank you, Newgate