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