I hope you have a lot of money.
For graphics design, you're pretty limited in your choices. The Macbook Pros are the obvious choice. They're readily available and come with screens calibrated for 100% sRGB color space coverage. Dell, Lenovo, and HP all have graphics workstations with optional screens that can cover 100% sRGB or even AdobeRGB. But they cost the same or even more than the MBPs. Look for the laptops with a Sharp IGZO screen - those tend to hit 100% sRGB or close to it. The Dell XPS 15 pretty much matches the 15" MBP. The HP Probook and Thinkpad W5xx have options for AdobeRGB screens, but are a lot chunkier.
If complete sRGB color gamut coverage isn't necessary, then lots of PC laptops will work. Typical laptop screens will manage about 70%-80% sRGB, which is probably unsuitable for graphics work. The good ones will hit 90%+ sRGB (a lot Sony's high-end models fit here), which for a student will probably be fine. But for professional use, you don't want a client refusing to pay because the color you delivered didn't exactly match the color he specified. Another option is to get a laptop with 80%-90% sRGB coverage for mobile work, and a 100% sRGB or AdobeRGB external monitor for final adjustments. Notebookcheck publishes sRGB coverage graphs with their reviews, but nearly every one is biased yellow-green which makes me suspect their colorimeter is out of whack. Mobiletechreview also usually tests sRGB coverage.
You'll need to buy a colorimeter too, or borrow one from a friend. If you get a MBP, you can probably get away without one - Apple color calibrates the screens before they box them. But the screen colors will drift over time so you want to recalibrate it now and then. I don't think any of the PC laptops come calibrated out the box. The Spyder 4 and XRite i1Display are both good relatively affordable choices.
(Note: I despise Apple's lock-in business strategies. So the fact that I'm recommending the MBPs really tells you something. Graphics artists and photographers are Apple's bread and butter customers and they've been designing computers to cater to their needs for over 2 decades. The MBPs are your best one-stop shop if you work in those fields. Avoid the Macbook Airs - those have terrible screens which barely manage 60% sRGB.)