Ideal for protecting the beginning and the end of a magnetic tape. Also useful for didviding the tracks recorded on the tape.
Colour versions were used in a home Hi-Fi and semi-professional domain, striped versions in broadcasting stations and recording studios.
Different marking schemes were used all over the world. It means that red stripes in one studio were used for stereo recording, in another one it signalised the 15 ips/38 cm/s speed.
You may find interesting German leader tape colour scheme table too.