I'm going to chime in here again with three options:
My personal option: Keep LG, if the noise returns then I'll document it. If the issue carries on then take it into the Apple Shop.
2nd option: Return both, telling them that they both have defects. It might not work which is why my personal option is listed above. Noise issue could be hard to replicate, Samsung machine would be easily replaced. Return LG, and fix Samsung.
3rd: Keep Samsung, this is it everything else fails. I'll just have to suck it up and enjoy it. It's still a beautiful machine.
If you think there is yellow tint then you don't need to show us. If you think it's unacceptable then rule it out. We don't need to tell you that, since you pretty much know that yourself.
Furthermore, I'd be 100% content with the LG right now. If the sound issue replicates then I would make my way to get it fixed, I'm sure it's not a huge problem and if it gradually gets worse then it'll be easier to replicate and fix. There's nothing wrong with the machine right now.
If you really want to keep the Samsung, then do it. But I would personally keep LG, and it anything 2nd option.