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