As Robert mentioned, an old scanner has problems. I remember a similar issue and the results were more red. The pcb inside close to the scanner itself(I assume) has some ICs than can degrade casuing the balance to be off. The downright failure of any of these cause some color disordination(?) or such and really if you can find the ICs, etc. you're lucky. At the time, a defect was related to the problem mentioned above and warranty covered the issue. But in your case, SOL. I can only suggest further, you clean any contacts, etc. for best operation. If no bulb, an LED array, check operation. Weak solder joint too, resolder for 100% contact. Play away... 
tada -----Willy 