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