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