The first four stripes on a wall with 100 stripes are red , blue, white, and purple. The four colors repeat in the same order. This means that Red always follow blue which is followed by white and then purple. This means that red would always start each new and consecutive set of four stripes and purple will always end it
We want to determine the 55th stripe. The last four stripes that include 55 ends with the 56th stripe. This means that the 56th stripe is purple. Therefore, the 55th stripe would be white because it follows purple.