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