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