OsSetPrimitiveParams

// change target_uuid to any uuid of the prim you wish to change visibility by clicking.
string target_uuid = "69031c69-36a5-4031-bdc8-8ca8c37f8eda";
vector default_color;
 
default
{
    state_entry()
    {
        list prim_params = osGetPrimitiveParams(target_uuid, [PRIM_COLOR, ALL_SIDES]);
        default_color = llList2Vector(prim_params, 0);
    }     
 
    touch_start(integer number)
    {
        list rules = [PRIM_NAME, "HIDDEN", PRIM_COLOR, ALL_SIDES, default_color, 0.0];
        osSetPrimitiveParams(target_uuid, rules);
        state alpha;
    }
}
 
state alpha
{
    touch_start(integer number)
    {
        list rules = [PRIM_NAME, "VISIBLE", PRIM_COLOR, ALL_SIDES, default_color, 1.0];
        osSetPrimitiveParams(target_uuid, rules);
        state default;
    }
}