Pink and Bramble are siblings
Snow is a former kittypet turned rouge and their friend
Bramble's eye colour is blueish purple
Pink and Snow's eye colour is greenish blue
Their book descriptions go as follows:
Pink- orange she cat with pinkish peach tabby markings with greenish blue eyes
Bramble- brown tabby she cat with white markings and pale indigo eyes
Snow- pale silver she cat with white markings and Aqua blue eyes
