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)(13,14)(15,17)(16,19)(18,20)(21,22,25,26)(23,24,28,27)(7,12)(10,11)(13,14,17,15)(16,19,20,18)(21,23)(22,24)(25,28)(26,27)(6,9)(10,11)(14,15)(16,20)(22,26)(23,28) involution — undirected(1,2)(3,4)(5,6)(7,10)(8,9)(11,12)(13,15,17,14)(16,18,20,19)(21,23)(22,27)(24,26)(25,28)(5,7,8,12)(6,10,9,11)(13,16,17,20)(14,18,15,19)(21,24,25,27)(22,23,26,28)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.