Kolams are not drawn during the observance of theetu period, some follow the practice of not drawing kolams for 40 days or until the first masyam or for 6 months. There are certain festivals like Srijayanti for which one should perform Tiruvaradhanam for Perumal, A couple of bakshanams can be prepared and offered to Perumal. Lighting lamps for Perumal are allowed during Thirukkarthigai. Those who do Makarasangramana Tharpanam have to continue them. So, celebrations can be done on a small scale.
It is up to an individual’s mindset in terms of not drawing kolams for one year, some start them on an auspicious day after the theetu period. Observing a period of sorrow is based on one’s closeness towards the departed.