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