Here is the original thumbnail:
But when uploaded to ThemeForest, it became darker as this:
It seemed to happen to PNG format only (the thumbnail needs a bit of transparent around). I’ve tried JPG format for other thumbnails and they worked just fine.
Do you have any suggestion about this?
I’ve noticed that too with some of my thumbnails. Uploading the thumbnail again usually fixes it.
I faced the same problem twice and solved. Both the occasions I noticed my thumbs contain gray scale colors only (just like yours)
Reuploading used to work for me too but this time it didn’t. Weird.
Wow, thanks for the tip! I’ve added a colored 1px dot in the thumbnail and it works now!