As mentioned by the CBSE, it is not bounded to carry a colored printout of NEET Admit Card.

But, it is necessary to download the NEET Admit Card because no candidate will be able to appear the examination without an Admit Card. The NEET Admit card can be downloaded by the candidate by entering their Roll Number and Date of Birth.

Know More - NEET Admit Card 2019

I would suggest you carry a colored print out of the Admit Card because the details are more clearly visible in the colored printout.