You can create this look by getting yourself a beaker filled with water, ideally you will start with a white for a base colour, you will then continue to drip any desired colour, in this case it was red, wait until it expands and then add your next colour, continue to do so until you have plenty of colours.
You will then need to grab yourself a tooth pick and drag this through the varnish to create a design, making sure to only drag from the second colour as it will all bundle up if dragged from outer colour.
You may want to put tape around your finger nails to avoid a big clean up after.
Dip your nail into the pattern, and keep under-water until you have collected the remaining varnish onto a Q-tip so it doesn't spoil your pattern when you remove it from the water.
Wait until dry, remove tape and clean up around edges with nail varnish remover.