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