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