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