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