What's with the colored tabs?

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The other day I downloaded IE-8 just to see what it's all about. So far I don't really see much difference, other than the tabs changing colors all the time. I've seen them be blue, yellow, green and purple. I don't know why they're changing like this or how to make them be just one color - I'd prefer green if I could do that. I'll probably look around in the preference later today and see what I can find. Has anyone else upgraded to IE-8 and noticed this? Please don't respond if you want to tell me what a peice of junk IE is and to use Firefox or something - I've tried them and for me IE works best.