So I tried for a few days and I can say that it is not the easiest to get to two drops collide, specially when you do not have the tools. Those who take really nice pictures of water droplets they have advanced tools like solenoid valves that emit a certain number of drops and a lot of lightning with different gel filters on them, so they get cool colors of the drops and the water in general. Do try, it is fun, but expect that it will be many hours of experimentation before you start getting into something decent.
I used a flash and some different backgrounds for my pictures. You can make such images, even if you don't have external flash but then very strong lights are needed instead.
camera equipment I used: Nikon 3ds, D90, tamron macro lens sp 90mm f 2,8 di, nikon speedlight SB900 and tripod.
Click on a picture to enlarge them!