The brake fluid I use is a very light gold. Red fluid is most likely Automatic Transmission Fluid (ATF), but a lot of power steering systems use ATF too so it could be either. iamwiz82 is certainly right that the tranny is far and away the most likely source.
You have to look at them, but unless they are platinum plugs (100,000 mile service life) they should be changed on a 20,000-30,000 mile interval. As for being hard to replace, that depends entirely upon the car. It's a 15 minute job to change all four in my Honda, but it's easily 45 minutes to an hour to change the four in a subaru (you have to remove the airbox). On Chevy S10 V6's you need to take off the front wheels (or so I've heard). General rule is that if the car is newer, the plugs will be a PITA to get at. There's just so much crap stuffed under the hood of modern vehicles that you can't change the plugs as easily as you once could.
It's the transaxle (technical term for the transmission in a front-drive car). From where you say it's leaking it might be the seal where the transaxle housing meets the engine block. To replace it you'll have to pull the transmission off of the car (not recommended for anyone other than an experienced mechanic), plus you'll probably have to have the rest of the transmission checked over, probably they'll tell you that you need a rebuild.
I've got a bottle of gold DOT 3 brake fluid sitting in the front trunk of the 914 which would dispute that. I've only seen specialty brake fluids that were red or purple, and I highly doubt that he's got specialty (read: expensive) brake fluid in his car.
