I always found that blue screen was Windows thing, but I came across the same problem in Ubuntu 16.04.3 LTS.
I’m sure this simple sequence of commands will help a lot of people to fix the error.
Leaving The Blue Screen On Ubuntu Login
Usually this problem is caused by some update, which corrupts something. First of all, your PC should have access to the internet, either via cable or WiFi.
At the login screen of Ubuntu, before entering the password, we will switch to the terminal mode, as follows:
Still on the login screen, press the key sequence: Ctrl + Alt + F1
Enter your login and password.
Then enter the commands below:
sudo dpkg –configure -a
sudo apt-get upgrade -f
sudo apt-get autoremove
sudo apt-get upgrade
Ready, after reboot, everything will be ok again.
I noticed that it is a very common problem, but can be fixed with with a simple solution, so I decided to share the solution.
Hope this helps.