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