Hi,
Very Sorry about the thread, it must have got deleted during the 2 hour downtime yesterday as hosting company was upgrading to latest OS.
The blue image in sidebar is just a placeholder image, it appears when you do not have set a featured image.
It’s location is Theme folder -> img folder -> sidethumb -> default.png
You can browse to this location using ftp software like filezilla.
You can replace it with same name image and size of 60 x 42px