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