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