Hi
Can you post the link so we can see the pic?
I have made soap like you suggested, here is how I did it.
I used an ordinary log mould. And I suggest doing each layer in separate batches so that you can get a straight line. Other wise the colours may go into each other depending on how thick you pour the soap.
So, just make a batch 1/4 of your normal size (if you want to have four different colours), pour that soap, let it set, do your next batch, pour and let it set, and so on and so on.
I would definitely recommend doing it in stages over a couple of days so that you get that nice crisp line. Also, you may have to spray the top of each layer with some alcohol immediately before pouring the next layer so that they adhere to each other. Another hint there is to have the mould warming in the oven as you are preparing the next layer, the soap seems to meld better when it is warmed a little.
So really you just need to chose your fragrance, something like monkey farts would be good, then your colours: yellow, red, blue, green, or whatever you want.
Please please post pics when you're done!
Hope I've helped some.