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