My '16 CR-V was White Diamond Pearl. The plastic front and rear bumpers had a yellow tint compared to the rest of the car from the factory. My brother's '16 Civic is the same. Seems like metallic/pearl paints (particularly lighter colors) look different on plastic and metal.
My 2006 Redrock Pearl has had the front and rear bumper covers fade to a bronze color. It is only these two plastic pieces that have done so, so I think it has something to do with the flexible paint they use on those parts.
This is because the factory mixes up a batch of paint say say NH757-AH. They whip up a 1000 units of whatever they are running at the manufacturer. Then they put in an order for a 1000 front and rear covers at the bumper factory. Since these factories are painting at different locations, humidity levels, Temps, etc. They have variances in the paint finish. So after the first 200 are made and installed they may get a call from the assembly plant saying they might try variance BH because the first 200 are a little dark or light. So they get it close but almost every car has different shades on the urethane bumpers. Ford is horrible. Also the metallic flakes react on urethane differently than on metal panels. It's called Flop. Cars get an e-coat below the primer that prevents rust but also charges the metal and the flakes stand up in the paint. They flop on the urethane though and reflect the light differently.