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)(15,19)(16,20)(17,18)(22,26)(23,28) involution — undirected(2,4)(6,9)(10,11)(14,18)(19,20) involution — undirected(1,2)(3,4)(13,15,17,16)(14,19,18,20)(21,22,25,26)(23,27,28,24)(5,7,8,12)(6,10,9,11)(13,16,17,15)(14,20,18,19)(21,23)(22,27)(24,26)(25,28)(5,6)(7,10)(8,9)(11,12)(13,14)(15,19)(16,20)(17,18)(21,24,25,27)(22,23,26,28)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.