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