Transparent picture boxes?

[Matt]

I don't want 100% transparent on the whole thing..

Just want it to not show a certain color, if you know what I mean.

Like, here is my example..

RRRRRRRRRPP
RRRRRRRPPPP
RRRRRPPPPPP
RRRPPPPPPPP
RRPPPPPPPPP

R = Red
P = Pink

I want it to take out all the Pink pixels, so it just look like this:

RRRRRRRRR
RRRRRRR
RRRRR
RRR
RR

So that way, it shows w/e background I have behind it in place of the pink pixels.

Anyone know how to do this?