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)(15,16)(17,25)(18,27)(19,24)(20,22)(21,26)(23,28) involution — undirected(5,7)(6,9)(8,12)(10,11)(13,15,19,26)(14,21,24,16)(17,18,20,28)(22,27,25,23)(2,4)(7,12)(9,11)(13,16,17,23,19,21,20,27)(14,15,25,28,24,26,22,18)(6,10)(9,11)(13,17,19,20)(14,22,24,25)(15,18,26,28)(16,23,21,27)(13,18,17,15,19,28,20,26)(14,23,25,21,24,27,22,16)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.