Bishop Promotion Curiousity

I'm not fully acquianted with all the rules of chess but whenever a pawn becomes available for promotion on a light square can it be promoted to a dark squared bishop or only a light squared bishop?

Its color is dictated by the color of the square it promotes on, I believe

@OP: The Pawn turns into a Bishop immediately upon entering the promotion square, and at that point the Bishop is committed to being either a light- or dark-square Bishop, depending on the color of the promotion square.

The bishop is the only piece that can't change color?! NOOOOOOOOOOOOOOOOOOOOOO! haha...thanks!

No peices can change colour, however all but the bishop can use both colours of square.

good tip. 

Why promote a pawn to a bishop, when a Queen does everything a bishop does and more?  The only piece you'd ever want to underpromote to is a knight, and that's a rare occasion.  

To avoid a stalemate, and no a knight isn't the only piece.

For example if you have a knight and pawn, and promoting to a heavy piece would give stalemate you need to promote to a bishop.

Having once reached this position, my opponent said he wanted to practice his two bishop checkmate technique!

What did you say? I wouldn't have been able to help myself: "Remember, you've only got 50 moves"

@Scottrf: That's a great example! I always have difficulty thinking of a realistic example necessitating a Bishop underpromotion.

Promoting to a Rook is more obvious:

@OP: One cannot promote to a Pawn, because the status of the unit would remain unchanged, and hence wouldn't be a promotion. The official rules state that a Pawn that reaches the eighth rank cannot remain a Pawn. It would be useless anyway if it did, except as a horizontal blockade, but any promoted piece can serve the same blockading purpose.

Also r.e. underpromotion to rook is the Saavendra position (quite a few with the same idea in TT).

That's an interesting position Scott, thx for that one.  

I have never in my life had to underpromote. Just sayin'.

There is a practical instance where promoting to Bishop can be useful: Say the promote square is covered by an enemy piece, you might want to hope that they don't just sac a piece for the pawn if you promote to a Queen, but rather give you a light or dark square grip (obviously depending on the colour of the promoted Bishop) by ignoring the Bishop.

Most of the time you would rather they just sac the piece however :/

There are endgame studies where you need to promote to a rook instead of a queen to avoid a stalemate.