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