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