Inclusion Criteria - Participant must previously untreated, histologically confirmed recurrent or metastatic colorectal adenocarcinoma, not amenable to curative surgery. - Participant must have no known presence of mismatch repair deficient (dMMR) or microsatellite instability-high (MSI-H) colorectal cancer (CRC) per historical results (a validated test should be used). - Participant must have no known presence of the gene that encodes the protein B-Raf (BRAF) V600E mutation per local testing. - Participant must have measurable disease as defined by Response Evaluation Criteria in Solid Tumors (RECIST) v1.1. Exclusion Criteria - Participant must not have any untreated known central nervous system (CNS) metastases including brain, leptomeningeal and/or spinal cord compression. - Participant must not have any prior malignancy active within the previous 2 years, except for locally curable cancers that have been apparently cured and considered to be of low risk of recurrence. - Participant must not have significant cardiovascular disease, such as myocardial infarction, unstable angina, arterial thrombosis or cerebrovascular accident within 6 months prior to randomization, uncontrolled hypertension (≥ 160 systolic, ≥ 100 diastolic mm Hg) despite optimal medical management, or congenital long QT syndrome. - Participant must not have prior systemic treatment with an anti-PD-1, anti-programmed death (ligand)-1 (PD-L1), anti-PD-L2, CD137 agonists, or anti-cytotoxic T-lymphocyte associated protein 4 (CTLA-4) antibody, or any other antibody or drug specifically targeting T cell co-stimulation or checkpoint pathways or chemotherapy. - Other protocol-defined Inclusion/Exclusion criteria apply.