One vertex per element, one color per generator, with an edge from x to x·s.
(5,6)(7,12)(8,10)(9,11)(13,14)(15,19)(16,21)(17,26)(18,22)(20,24)(23,27)(25,28) involution — undirected(1,2)(3,4)(5,7,9,8)(6,10,11,12)(13,15,18,23)(14,19,22,27)(16,25,17,24)(20,21,28,26)(2,4)(13,15)(14,20)(16,24)(17,25)(18,23)(19,26)(21,27)(22,28) involution — undirected(1,2)(3,4)(5,8,9,7)(6,10,11,12)(15,23)(19,27)(20,28)(24,25)(2,4)(13,16,18,17)(14,21,22,26)(15,24,23,25)(19,20,27,28)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.