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