This is a fast but cute little twist on a regular ponytail.
Start by pulling all of the hair tightly back into a ponytail and then grab some colored elastics to begin your design.
Grab a small section of the ponytail from the right side and tie a colored elastic around it about an inch down. Grab a section from the left side of the ponytail and do the same. Now combine the two sections with another colored elastic about an inch below the first two. Now grab a new section from the right side and a new section from the left side and put each into it's own colored elastic. Combine the two about an inch below with another elastic. Keep going with the pattern until you run out of hair and just secure all the ends together with one final colored elastic.