Thanks for the nice remarks folks
i did it after going out twice in the day and not getting any shots, sort of a lack of direction.
Here's how I took the shot;
1 pint glass full of water
Food dye and dropper
2 sheets of white paper
YN580 and triggers
Camera on a tripod, I used a 50mm lens
I put the pint glass on a piece of paper and place a piece of paper behind the glass as a backdrop. I placed the flash 6" or so behind the paper, zoomed out and the wide diffuser (sp) down.
I set the camera up on the tripod in portrait and used a coathanger upside down in the middle of the glass to focus and removed the hanger. I then played about with exposure and flash settings until I was happy, which turned out to be ISO100, f6.3, 1/200th, I'm not sure of the flash setting. I then set the camera to rapid fire and used a remote.
Next up was the dye into the water, I started off with blue and red but it went very wrong and mixed too much. In the end blue was the best colour for me and the best way to do the drops was to have the dropper as close to the surface of the water as possible.
That's it really, I did about four glasses of water and that was enough for two OK shots. In photoshop I made the background a uniform white and adjusted the contrast etc.
Good luck!