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