I went through 5 different paperwhites last month from Amazon.com and Best Buy before returning them all. I bought an iPad Mini and while I love my mini, I miss the use of an e-reader.
I took a chance and bought a Paperwhite from Staples Black Friday sale. Like "New", I don't see any color blobs. The shadows are still there, but it's not as bad as the previous ones. The screen looks real sharp with the light down. With the light all the way up, it's the best I've had.