In national tournaments (swiss style) do you always alternate colors?

For an extremely large swiss-style tournament, like the nationals, do you alternate color from game to game?  Say if game 1 you are white, does that mean you are sure to be white for game 3, 5, etc.?  Or can it go randomly, like 2 straight games as black, then 2 as white.

Also, what happens if you get 4 blacks out of 7 games?  Does that factor into tie-break rules vs. someone who got 4 whites?  (For USCF and FIDE)

they usually try to as much as they can even in small tournaments

I know they try, but is it possible to get 2, or even 3 blacks in a row?

In all the tournaments I played in, I only got the same color 3 times in a row once.

Whoa, somebody else keeps bleeding through on this station...

There should be a rule that says you can't get the same color 3 times in a row.  2 games, I could understand, due to matching difficulties.  But 3 times, why don't they just get someone else instead of the same person again?