Laptop has bad backlight. How can I tell if it's the screen or board?

Before the backlight went out, the screen's colors were very distorted. Although, when the computer was plugged into an external monitor, everything appears fine on the external monitor. Eventually, the screen just gave out and now nothing seems to show up on it unless I point a flashlight behind it and then it becomes very dimly visible. How can I tell whether the board is at fault or if its the screen itself? I'm thinking it might be the screen because the colors were distorted and also the LCD connector cord attached to the screen looks a little off and out of shape. This one is also really hard to put on compared to ones that I have worked with in the past.

So, how could I determine whether the board is the problem or the screen?