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