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