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