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