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