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