Are you referring to the display in general? This is a common occurrence over the history of the iPhone. Some production runs seem to have displays that are 'warmer' than others. My iPhone 5s definitely had a warmer (yellow) tint when compared to my iPhone 5 (cooler).
If it really troubles you, you could make a Genius appointment. At a minimum, you could confirm that your iPhone 5s is exhibiting normal behavior.