Laptop monitor samsung R40 flickering and showing nothing but blue white colors. I connected the laptop to an external monitor and the laptop works. is it the source of the monitor the problem?

If the external monitor works fine then most likely there is nothing wrong with the motherboard or video card and the problem is somewhere inside the laptop display panel.

Here's what I usually do in order to narrow down problems like this:

1. I reseat the video cable connectors on both ends, on the motherboard/video card and on the back of the LCD screen. If the video cable gets loose, it might cause a problem like on your laptop.

2. Replace the video cable

3. Replace the LCD screen