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