I have no idea, since I never go to MTGNews and don't know when they had their site "look" like this.
The CPA went to this color scheme in the fall of 2000 (almost a year ago, I believe). but even when it was orange and black, the layout was pretty much the same.
You'd have to ask Ed for sure, but I think it's because they both use the same software... VBulletin. the CPA just upgraded to 2.0, but MTGNews was upgraded a while ago. (I believe)
Not sure about the colors, I guess they just work the best...
I have only been at mtgnews since May and here for about a week. Each site had pretty much the same style, but they were both like that when I arrived.