Hey Shruti, 4 Days itinerary : Day1: Delhi to Mathura ( 3 hours ). Local sightseeing- Dwarkadheesh temple, Sri Krishna Janma Bhumi, Vishram Ghat and Radha Kund Day2: Mathur to Vrindavan. Local sightseeing - Banke Bihari Temple, Sri Radha Raman Mandir, ISKCON Temple, Prem Mandir Day3: Vrindavan to Agra. Local sightseeing- Taj Mahal and Agra Fort Day4: Agra to Fatehpur Sikri. Local sightseeing- Buland Darwaza, Salim Chishti's Tomb and Panch Mahal. Fatehpur Sikri to Delhi. Happy travelling!!!!!!!
I would suggest to book early for hotels as these will get costly as time lapses further if you really want to enjoy the holi of Vrindavan and Mathura please go for lathmar Holi though it will consume your hole day but you fill find it worth. Further Agra and Fatehpur Sikri is not far away you can explore these places. Happy Travelling!!
As other people already replied for itinerary so I'm gonna give a few tips.
It's a good idea. First, decide that which place and time you're coming here because Holi is started. I recommend you to visit Nandgaon and Barsana hold if you are coming here for the first time. Your trip will be blast Because people come here across the globe. You'll face a heavy crowd in Holi celebration and need to put your camera in your bag or pocket. Because it is very risky to handle it while you're stepping to Temple in a heavy crowd.