A Study to Evaluate the Safety and Efficacy of Two Dose Levels of ONO-4578 With Opdivo®, in Combination With mFOLFOX6 and Bevacizumab Versus Standard of Care in Participants With Non-MSI-H/dMMR, PD-L1 Positive Advanced Colorectal Cancer

Required: PD-L1 (CD274) positive expression (positive)

Participants whose tumor is positive for PD-L1 expression as determined at a central laboratory

Excluded: BRAF V600E

Participants with BRAF V600E mutation

Excluded: MSH2 deficient mismatch repair

mismatch repair deficient (dMMR) tumor

Excluded: MSH6 deficient mismatch repair

mismatch repair deficient (dMMR) tumor

Excluded: MLH1 deficient mismatch repair

mismatch repair deficient (dMMR) tumor

Excluded: PMS2 deficient mismatch repair

mismatch repair deficient (dMMR) tumor

Excluded: MSI high microsatellite instability

Participants with high microsatellite instability (MSI-High)

Cannot have received: anti-PD-1 therapy

Prior treatment with an anti-PD-1, anti-PD-L1, anti-PD-L2, or anti-CTLA-4 antibody, or any other antibody or drug specifically targeting T-cell co-stimulation or immune checkpoint pathways.