NaCN does discolor and degrade over time with exposure to air. Even if the coloration is fairly extreme, it can still be used for many purposes as is. For example, a 50 year old bottle of grey-brown degraded material sealed with a dry rotted cork and bakelite cap reacted fine with a certain substituted benzyl chloride. An excess was used to compensate for possible decomposition.
I know you probably know this but I'm going to say it anyway. This shit is rediculously toxic and dangerous to work with in basement laboratory conditions. If you decide to risk it, remember that most reactions involving NaCN will emit HCN fumes. Many authors neglected to report this fact in much existing reference material using this reagent. If you do decide to live dangerously and work with this shit, make sure you have some of those amyl nitrite poppers around. If you get a face full of HCN (trust me, you'll know if this happens- it has a horrible smell and smacks you in the face like a ton of bricks) inhaling 2 or three of those poppers over a several minute period may save your life. If you spill a solution of that stuff on you, you're in deep shit. The antidote is sodium thiosulfate and sodium nitrite solution, but it must be administered intravenously. I dont think oral absorbtion would be quick enough to save your ass.