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