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