So I just noticed today when I access the menu, the bottom 1 and a half lines are brighter then the rest of the screen. When scanning it is the same way. The white letters at the bottom are brighter then the ones at the top. The attached picture is how it looks with a white background. Notice the difference ?
Sadly, there is no perfection when it comes to the SDS series; whether this is caused by parts they are interchanging during production from various sources, or other reasons. I have access to several SDS100 units, as well as SD200 units, and they all have their own minor idiosyncrasies from unit to unit. If it is bothering you to the point of distraction, and this unit is new and within your return window, you might consider returning it for a refund (not an exchange), and then buy another unit from a different dealer.
As a417 mentions above, sending it back to them might get it repaired, but as he states, others have gotten back their units with either the same issue or with other anomalies.
You would expect (or at least hope) that at 600 or 700 USD, you would get a unit with no imperfections; this is not the case. By the way, you mentioned that you "just noticed today"--- do you suspect that this condition developed suddenly? Have you tried color combinations on your screen and is the result similar?