Try the hard reset, but that probably wont work. You probably need a new screen. You may have a short in the cable for your screen, or some of the backlight bulbs could have burned out. Also, If it's damaged from water, a new screen likely wont help.
I don't know which Kindle you have for sure, so double check for compatibility, but here's a replacement screen on eBay for about $50: http://www.ebay.com/itm/Replacement-LCD-DIsplay-Screen-E-ink-For-Amazon-Ebook-Kindle-4-ED060SCF-LF-C1-/281157987327?pt=LH_DefaultDomain_0&hash=item4176526bff
You can find a repair guide video by clicking on the Kindle picture. I'm sure they have more screen replacement guides on the internet as well.