I read on OnePlus One website : "If your device has more than 3 dead pixels or if the dead pixel is greater than 0.15mm in size, we can offer a replacement."
Hi
Any warranty is out the umi control. Whole warranty process needs to be done between customer and reseller. Sometimes is cheaper buy screen your self and replace than pay shipping to reseller.
Or, even better, buy from Amazon. I bought my first Max from Amazon, which developed a fault after two weeks. Amazon replaced the phone immediately, without any costs incurred.