A Study of Nivolumab Alone or Nivolumab Combination Therapy in Colon Cancer That Has Come Back or Has Spread

Inclusion Criteria: * Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 1 * Histologically confirmed recurrent or metastatic colorectal cancer * Measurable disease per RECIST v1.1 * Microsatellite instability expression detected by an accredited laboratory * Participants enrolled into the C3 Cohort must have not had treatment for their metastatic disease Exclusion Criteria: * Active brain metastases or leptomeningeal metastases are not allowed * Prior treatment with an anti-Programmed Death Receptor (PD)-1, anti-PD-L1, anti-PD-L2, anti-Cytotoxic T-Cell Lymphoma-4 Antigen (CTLA-4) antibody, or any other antibody or drug specifically targeting T-cell co-stimulation or immune checkpoint pathways * Prior malignancy active within the previous 3 years except for locally curable cancers * Participants with active, known or suspected autoimmune disease * Participants with a condition requiring systemic treatment with either corticosteroids or other immunosuppressive medications within 14 days of study drug administration Other protocol-defined inclusion/exclusion criteria apply