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