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