With a 56 percentile in JEE Mains, securing a Computer Science (CS) seat in top-tier colleges like NITs or IIITs is generally challenging due to high cutoff ranks. However, you still have opportunities in various other engineering colleges across India. Your percentile suggests that your rank will likely fall in a range where admission to many private and some state government-affiliated colleges is possible.

Several private engineering colleges consider JEE Main scores for admission. These colleges often have a wider range of cutoff percentiles. Some examples include: Seacom Skills University, Accurate Institute of Management and Technology (Noida), Terna Engineering College, Pallavi Engineering College, Marwadi University, and RK University. These are just a few names, and many other similar institutions might be available depending on your location and preferred course fees.

State government colleges can also be an option. While the top ones might have high cutoffs, some affiliated colleges could admit students with your percentile, especially in less preferred branches or through state-level counseling. It's advisable to research the specific state engineering colleges in your region (like West Bengal) and check their admission criteria and previous year cutoffs. Keep an eye on the state-level counseling processes, as they often have different cutoff criteria.

When exploring these options, consider factors beyond just the possibility of getting a CS seat. Look into the college's infrastructure, faculty quality, placement records, and the overall learning environment. It might be beneficial to also consider related fields like Information Technology (IT), Computer Engineering, or even Electronics and Communication Engineering (ECE) if your primary interest is in the computing domain, as these fields often have overlaps in curriculum and career opportunities.

I hope it helps.