Spiderman said:
			
		
	
	
		
		
			Thanks!
Really?  The commons are distributed like that?
		
		
	 
If there are no common Artifacts, multicolors, or lands, then you usually will see a cycle of colors followed by another cycle of colors, followed by a card the same color as the first.  When there's other types - then it's more random (I think they include some of those in the color stacks.  I think they started doing it for more consistency in Limited in terms of spread out colors.  too often you'd get 4 or 5 of one color and none of another.  That gave that player an unfair advantage sometimes because they could use fewer colors to a better end.
It's been that way for a long time (watch when you open a pack - I think they usually follow the color order WUBRG)  The next pack should pick up where the previous left off would be my guess.  So, if a pack ends on R, the next starts with Green.  Foils mess everything up of course...  but for our purposes - no foils.  
I think they completely randomize the Uncommons - because I've gotten 3 of the same color before in one booster.  And of course the Rare is completely random - though in a box you tend to get different ones...
How I generate a box is to create a complete set, rotate through the commons - give 3 uncommons and one rrare.  For the next booster I pick up in the commons where I left off.  If I had to generate a ton of packs, I'd re-randomize commons when the first "set" ran out - but continue with Uncommons and rares until I ran out of those.  I think that's how Wizards does it - but I don't think they talk about their process (if they do I haven't seen it, though I don't frequent wizards.com anymore - only when a stray link from here piques my interest).
Back in the days of revised - remember the "sheets".  they even provided some sheets for sale once or twice.  Back then they used to only be able to make sheets of one size - which was how lands got mixed in the Uncommons I think.  By the time of Ice Age or so is when I think they moved from Carta Mundi to another plant which offered more flexability with print runs.  (from my recollection of a duelist article from way back when).