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