Laptop screen has colored vertical lines running through it

Definitely not the inverter. It could be the cables between the display and the mainboard / Graphic card, but most likely you need another display. Have you tried attaching an external monitor just to make sure it isn't the graphic card?

I would say if ruling out the graphics card, a GOOD possibility would be the ribbon cable connecting the display to the motherboard... I would try replacing that before replacing the screen

I would look at the flat cable and clean it with a clean eraser . And blow out the cable conectors with some compressed air .

All so you can use a Multi Meter and ohm the flat cable to test it.

It sounds like your lcd is bad.

I put an external monitor on the laptop and the picture wa perfect on the external monitor...  no lines.

So that leaves you with the cable and Display itself.

Moret than likely it is the cable that connects the lcd to the motherboard. You can find them on the internet and order them. They are expensive though because they are labor intensive to make. The other thing that you could try is the lcd. Since you dont have any parts that you can use to test which item it is, I would order the cable. It is the only thing that is subject to wear and tear from opening the lid.
The thing that you might not like or be capable of is replacing the cable. IT is not for the meak. You have to take the lid apart and remove the lcd to get to the back of it and you have to remove the bezel and the keyboard to get to the motherboard connections.  Lots of small screws and patience is needed.

I would put my money on the inverter.  A simple way to know exactly what it is, is to download and burn the diagnostics cd from support.dell.com for your laptop.  It will tell you the exact error code that is failing.  From there you can google and ebay your way back to a good screen.

I will download the diagnostics cd from dell.   But will have to use an external monitor since the monitor cracked while I was removing it

Well this is for a customer.   I will get the number off the back and get the new screen.

Thanks