Two versions. First is for single prims, second for multiple linked prims.

default 
{
    state_entry() 
    {
        llSetTimerEvent(2.0); // every 2 seconds
    }

    timer() 
    {
        llSetColor(, ALL_SIDES);
    }
}

default 
{
    state_entry() 
    {
        llSetTimerEvent(2.0); // every 2 seconds
    }

    timer() 
    {
        llSetLinkColor(LINK_SET, , ALL_SIDES);
    }
}