Discoloration due to heat?

Is it even possible?

I use a silicon protector covering the entire keyboard and wrist area, along with the trackpad button.. so it's quite impossible to get dirt in between. But a few days ago, I noticed the left area of the keyboard was darker; specifically the areas around the letters QWE, ASD, and ZX.

Since I'm kinda paranoid about my MB, I removed the silicon and cleaned the area with wipes; and after a few minutes of rubbing and drying.. the dirt was gone. But still I noticed, the left area of the keyboard was still darker than the right area. The right area was spick and span compared to the left. Is the darkening caused by heat and overuse?

Just yesterday night, I noticed while typing that the left area of the keyboard was warmer than the right. I knew that the battery was there, but the battery was below the wrist area, not the keyboard right? So why is it sort of warmer than usual? Or am I just paranoid?

I use the iStat Pro widget to see my temps. In CPU A, my usual temparature is 60-64º. Heatsink A is 57º-58º, Heatsink B is the same. Enclosure bottom is 37º. Northbridge 1 and 2 is at 55-56º. Membank A1 is 53-56º. The hard drive is at 43-45º.

Is the iStat Pro accurate? What's the normal temperature of the MB? Again sorry for the long post. I just try to give as many details as I can. Thanks in advance.

The left side of my MacBook gets warm when connected to a power source or if I have my iPod hooked up. Not sure if it's something to worry about however your temps do seem a little warmer than mine - of course this is dependent upon what you're doing with your MacBook - at the time I took this screen dump I'd not really been doing too much with the MacBook, it has been awake for about 90 minutes but only used for web browsing and email checking so far.

You do say that you have a Silicone cover over your keyboard; the gaps under the keys allow air to circulate I believe, perhaps your cover is keeping too much heat within the MacBook.

The attached image is from iStat Pro

Yes, it does seem that my temperature's high. The time I checked that, I was running Yahoo Messenger, iTunes, and Safari. And Speed Download I think.

Do you think the silicon's harming the MB? It's weird, I've noticed the heat just recently.. but the cover's been with me for months.

One question's still not answered. You think the heat's causing the slight darkening of the spaces around the keys?