One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,4)(13,14)(15,22)(16,20)(17,26)(18,21)(19,25)(23,28)(24,27) involution — undirected(5,6,8,9)(7,10,11,12)(13,15,18,23)(14,19,21,27)(16,25,17,24)(20,28,26,22)(2,4)(6,9)(7,11)(15,23)(19,27)(22,28)(24,25) involution — undirected(5,7)(6,10)(8,11)(9,12)(13,14)(15,19)(16,26)(17,20)(18,21)(22,25)(23,27)(24,28) involution — undirected(6,9)(7,11)(13,16,18,17)(14,20,21,26)(15,24,23,25)(19,22,27,28)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.