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