Thanks for your clarification. I think we need to know from someone who has it for more than 14 days if the yellowish problem is developed. The issue may not get noticed for the first few days, even I didn't notice it when I first received it.
I went into HN and had a chat with one of the salesman.
I initially asked about quality issues generally and he said they had none although a supply issue with the i7/512G not being able to get them. This is a different story to another salesman whose comments I posted earlier.
I then mentioned the yellow screen issue and he commented that it is a common problem across all devices they sell and is to do with bonding/gluing in compact devices. He said even the iPhone initially had this issue. He said because it is bonding related, yes it can get worse with time and use. He also blamed altitude and temperature changes during shipping as contributing causes.
This is no doubt a quality control issue albeit a common one as obviously if iPhones initially had this issue, they don't currently, so it is something that can be controlled by the manufacturer otherwise it would either show up randomly or constantly on all devices and that isn't the case.
I guess though your concerns of returning and getting another one are somewhat justified but I don't see any other alternative other than putting up with it.