回答“Why are colored lines running down my screen?”As Dan said, a functioning external display would indicate that the graphics chip is working, and therefore the problem lies with either the cable running to the LCD display or the LCD display itself. If you could take pics of your screen - say with your phone and post them, that would help us. Otherwise, and this is pure conjecture, it sounds like the screen (and/or its assembly is damaged). The screen is either THE most expensive part to replace, or the 2nd most expensive part to replace - the other being the main logic board. Given it’s age, I’m guessing we can assume it’s out of warranty. If you want to do the repair yourself, there is a guide listed here. The replacement is fairly straightforward. It’s the likely cost that you’ll have to consider. Good luck.
回答“Three monitor setup for Mac Pro 2008?”You can add a second graphics card to it. I have the same unit, though I'll be upgrading it soon. The second card I installed some time ago, is an ATI Radeon 5770 1GB. I checked, and it's available from Amazon through it's resellers. That card has a DVI port and two mini Display ports. It will drive two monitors simultaneously in addition to your original card driving a single monitor. Shouldn't be a problem. By the way, the card mentioned above is dual width. It'll fit in one slot, but it is huge - full length, full height, and it requires power from the motherboard. Read the docs that come with it. Eric J.